The LCM of two numbers is 2028 and their HCF is 25 if one of the number is 100 find the other

1. Two numbers are in the ratio 2 : 3. If their L.C.M. is 48. what is sum of the numbers?
A. 64B. 42
C. 28D. 40

answer with explanation

Answer: Option D

Explanation:

Let the numbers be $2x$ and $3x$LCM of $2x$ and $3x$ $=6x~~$ (∵ LCM of 2 and 3 is 6. Hence LCM of $2x$ and $3x$ is $6x$)Given that LCM of $2x$ and $3x$ is 48=> $6x=48$=> $x=\dfrac{48}{6}=8$Sum of the numbers$=2x+3x\\=5x$

= 5 × 8 = 40

2. What is the greatest number of four digits which is divisible by 15, 25, 40 and 75 ?
A. 9200B. 9600
C. 9800D. 9400

answer with explanation

Answer: Option B

Explanation:

Greatest number of four digits = 9999LCM of 15, 25, 40 and 75 = 6009999 ÷ 600 = 16, remainder = 399Hence, greatest number of four digits which is divisible by 15, 25, 40 and 75

= 9999 - 399 = 9600

3. Three numbers are in the ratio of 2 : 3 : 4 and their L.C.M. is 240. Their H.C.F. is:
A. 40B. 20
C. 10D. 30

answer with explanation

Answer: Option B

Explanation:

Let the numbers be $2x$, $3x$ and $4x$LCM of $2x$, $3x$ and $4x$ = $12x$$12x=240\\~\\\Rightarrow x=\dfrac{240}{12}=20$

H.C.F of $2x$, $3x$ and $4x$ $=x=20$

4. What is the lowest common multiple of 12, 36 and 20?
A. 120B. 160
C. 220D. 180

answer with explanation

Answer: Option D

Explanation:

The LCM of two numbers is 2028 and their HCF is 25 if one of the number is 100 find the other

LCM = 2 × 2 × 3 × 1 × 3 × 5 = 180

5. What is the least number which when divided by 5, 6, 7 and 8 leaves a remainder 3, but when divided by 9 leaves no remainder?
A. 1683B. 1108
C. 2007D. 3363

answer with explanation

Answer: Option A

Explanation:

Solution 1LCM of 5, 6, 7 and 8 = 840Hence the number can be written in the form (840k + 3) which is divisible by 9.If k = 1, number = (840 × 1) + 3 = 843 which is not divisible by 9.If k = 2, number = (840 × 2) + 3 = 1683 which is divisible by 9.

Hence 1683 is the least number which when divided by 5, 6, 7 and 8 leaves a remainder 3, but when divided by 9 leaves no remainder.

Solution 2 - Hit and Trial MethodJust see which of the given choices satisfy the given condtions.Take 3363. This is not even divisible by 9. Hence this is not the answer.Take 1108. This is not even divisible by 9. Hence this is not the answer.Take 2007. This is divisible by 9.2007 ÷ 5 = 401, remainder = 2 . Hence this is not the answerTake 1683. This is divisible by 9.1683 ÷ 5 = 336, remainder = 31683 ÷ 6 = 280, remainder = 31683 ÷ 7 = 240, remainder = 31683 ÷ 8 = 210, remainder = 3

Hence 1683 is the answer

Set 1Set 2Set 3Set 4Set 5Set 6

How to find out sum of numbers if their lcm given..?
plz . tell me

How to find out sum of numbers if their lcm given..?<br>plz . tell me

The product of two numbers is 2028 and their H.C.F. is 13. The number of such pairs is?

The product of two numbers is 2028 and their H.C.F. is 13. The number of such pairs is?

Since h.c.f. is 13, these numbers can be written as 13a and 13b.Now, according to the question, we have product of these numbers is 2028.Then, 13a × 13b = 2028.=> a × b=12Prime factors of 12 are 2,3.12 = 2×2×3.Number of factors of 12 =(2+1)(1+1)=6Since 12 is not a perfect Square, so we can express 12 in $\frac{6}{2}$ = 3 ways as a product of two numbers.

Hence, Required no. of pairs = 3 Ans.

Since h.c.f. is 13, these numbers can be written as 13a and 13b.Now, according to the question, we have product of these numbers is 2028.Then, 13a × 13b = 2028.=> a × b=12Prime factors of 12 are 2,3.12 = 2×2×3.Number of factors of 12 =(2+1)(1+1)=6Since 12 is not a perfect Square, so we can express 12 in $\frac{6}{2}$ = 3 ways as a product of two numbers.<p>Hence, Required no. of pairs = 3 Ans.</p>

Going by your argument, the 3 ways of expressing 12 as product of two number are12 = 1×1212 = 2×612 = 3×4In this, you can not take 2,6 because they are not co-prime. Suppose we take (2,6) thennumbers are 26, 78But HCF(26,78) is not 13.Generally, you can only take such pairs which are co-prime

(1,12) and (3,4) are fine and as explained by Jay, answer is 2

Going by your argument, the 3 ways of expressing 12 as product of two number are12 = 1×1212 = 2×612 = 3×4In this, you can not take 2,6 because they are not co-prime. Suppose we take (2,6) thennumbers are 26, 78But HCF(26,78) is not 13.Generally, you can only take such pairs which are co-prime<p>(1,12) and (3,4) are fine and as explained by Jay, answer is 2</p>

Take numbers as 13a and 13b (because 13 is the HCF)13a * 13b = 2028ab = 1212 can be written as a product of co-prime numbers in the following waysa. 1*12b. 3*4(i.e., two ways)So required number of ways = 2

The pairs are (13*1, 13*12) and (13*3, 13*4)

Take numbers as 13a and 13b (because 13 is the HCF)13a * 13b = 2028ab = 1212 can be written as a product of co-prime numbers in the following waysa. 1*12b. 3*4(i.e., two ways)So required number of ways = 2<p>The pairs are (13*1, 13*12) and (13*3, 13*4)</p>

If LCM of 15,20,X=180 then what is the value of X???

If LCM of 15,20,X=180 then what is the value of X???

Many values are possible.15 = 3*520 = 2*2*5LCM of 15 and 20 = 3*2*2*5=60(3*2*2*5) * 3 = 180ie, an additional 3 should be there to make the LCM 180

number can be 3*3=9, 3*5*3=45, 2*2*5*3*3 = 180, etc

Many values are possible.15 = 3*520 = 2*2*5LCM of 15 and 20 = 3*2*2*5=60(3*2*2*5) * 3 = 180ie, an additional 3 should be there to make the LCM 180<p>number can be 3*3=9, 3*5*3=45, 2*2*5*3*3 = 180, etc</p>

the HCF of 2 number is 98 and their LCM is 2352.the sum of the number may be

a.1372

b.1398

c.1426

d.1484

the HCF of 2 number is 98 and their LCM is 2352.the sum of the number may be<p>a.1372</p><p>b.1398</p><p>c.1426</p><p>d.1484</p>

X*y= 98*2352

X*y=98*98*12*2

X*y= (98*2)*(98*12)

As compair to x and y then 

X= 98*2

X= 196

Y = 98*12

Y= 1176

Then

X+y

196+1176= 1372

X*y= 98*2352<p>X*y=98*98*12*2</p><p>X*y= (98*2)*(98*12)</p><p>As compair to x and y then </p><p>X= 98*2</p><p>X= 196</p><p>Y = 98*12</p><p>Y= 1176</p><p>Then</p><p>X+y</p><p>196+1176= 1372</p>

In the question, 'none of these' is not given as an option and 1372 is the only number divisible by 98. So one can directly write the answer as 1372

In the question, 'none of these' is not given as an option and 1372 is the only number divisible by 98. So one can directly write the answer as 1372

1234

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Q.1

The LCM of two numbers is 864 and their HCF is 144. If one of the number is 288, the other number is :

576

1296

432

144

Ans .

3


  1. Explanation :

    Using Rule 1, Required number
    = LCM X HCF
       First number
    = 864 x 144 = 432
           288

Q.2

LCM of two numbers is 225 and their HCF is 5. If one number is 25, the other number will be:

5

25

45

225

Ans .

3


  1. Explanation :

    Using Rule 1, LCM × HCF = 1st Number x 2nd Number 225 x 5 = 25 x X

    X = 225 x 5 = 45


              25

Q.3

The L.C.M. of two numbers is 1820 and their H.C.F. is 26. If one number is 130 then the other number is :

70

1690

364

1264

Ans .

3


  1. Explanation :

    Given that L.C.M. of two numbers = 1820 H.C.F. of those numbers = 26 One of the number is 130

    Another number = 1820 x 26 = 364


                                     130

Q.4

The LCM of two numbers is 1920 and their HCF is 16. If one of the number is 128, find the other number

204

240

260

320

Ans .

2


  1. Explanation :

    Using Rule 1, We have, First number × second number = LCM × HCF

    Second number = 1920 x 16 = 240


                                     128

Q.5

The HCF of two numbers 12906 and 14818 is 478. Their LCM is

400086

200043

600129

800172

Ans .

1


  1. Explanation :

    Using Rule 1, Product of two numbers = HCF × LCM = 12906 × 14818 = LCM x 478

    LCM = 12906 x 14818

                       478

    = 400086

Q.6

The H.C.F. and L.C.M. of two 2- digit numbers are 16 and 480 re- spectively. The numbers are

40, 48

60, 72

64, 80

80, 96

Ans .

4


  1. Explanation :

    Using Rule 1, H.C.F. of the two 2-digit numbers = 16 Hence, the numbers can be expressed as 16x and 16y, where x and y are prime to each other. Now, First number × second number = H.C.F. × L.C.M. 16x × 16y = 16 × 480

    xy = 16 480 = 30

           16 x 16 The possible pairs of x andy, satisfying the conditionxy = 30 are : (3, 10), (5, 6), (1, 30), (2, 15) Since the numbers are of 2-digits each. Hence, admissible pair is (5, 6)

    Numbers are : 16 × 5 = 80

Q.7

The HCF of two numbers is 16 and their LCM is 160. If one of the number is 32, then the other number is

48

80

96

112

Ans .

2


  1. Explanation :

    Using Rule 1, We know that, First number × Second number = LCM × HCF Second number

    16 x 160 = 80


           32

Q.8

The product of two numbers is 4107. If the H.C.F. of the numbers is 37, the greater number is

185

111

107

101

Ans .

2


  1. Explanation :

    LCM = Product of two numbers              HCF

    4107 = 111

        37

    Obviously, numbers are 111 and 37 which satisfy the given condition. Hence, the greater number = 111

Q.9

The HCF of two numbers is 15 and their LCM is 300. If one of the number is 60, the other is

50

75

65

100

Ans .

2


  1. Explanation :

    Using Rule 1, First number × Second number = HCF × LCM Second number

    15 x 300 = 75


          60

Q.10

The HCF and LCM of two num- bers are 12 and 924 respectively. Then the number of such pairs i

0

1

2

3

Ans .

3


  1. Explanation :

    Let the numbers be 12x and 12y where x and y are prime to each other. LCM = 12xy 12xy = 924 xy = 77

    Possible pairs = (1,77) and (7,11)

Q.11

The LCM of two numbers is 30 and their HCF is 5. One of the number is 10. The other is

20

25

15

5

Ans .

3


  1. Explanation :

    Using Rule 1, First number × second number = LCM × HCF Let the second number be x. 10x = 30 × 5

    x = 30 x 5 = 15


           10

Q.12

The product of two numbers is 1280 and their H.C.F. is 8. The L.C.M. of the number will be

160

150

120

140

Ans .

1


  1. Explanation :

    Using Rule 1, HCF × LCM = Product of two numbers 8 × LCM = 1280

    LCM = 1280 = 160


              160

Q.13

The H.C.F. and L.C.M. of two numbers are 8 and 48 respec- tively. If one of the number is 24, then the other number is

48

36

24

16

Ans .

4


  1. Explanation :

    Using Rule 1, First number × second number = HCF × LCM 24 × second number = 8 × 48

    Second number = 8 x 48 = 16


           24

Q.14

The H.C.F and L.C.M of two num- bers are 12 and 336 respectively. If one of the number is 84, the other is

36

48

72

96

Ans .

2


  1. Explanation :

    Using Rule 1, First number × second number = HCF × LCM 84 × second number = 12 × 336 Second number

    = 12 x 336 = 48


           84

Q.15

The product of two numbers is 216. If the HCF is 6, then their LCM is

72

60

48

36

Ans .

4


  1. Explanation :

    Let the numbers be 6x and 6y where x and y are prime to each other. 6x × 6y = 216

    xy = 216 = 6

           6 x 6

    LCM = 6xy = 6 × 6 = 36

Q.16

The HCF and LCM of two num- bers are 18 and 378 respectively. If one of the number is 54, then the other number is

126

144

198

238

Ans .

1


  1. Explanation :

    Using Rule 1,
    Second number = HCF x LCM         First number

    18 x 378 = 126


    54

Q.17

The HCF and product of two numbers are 15 and 6300 re- spectively. The number of possi- ble pairs of the numbers is

4

3

2

1

Ans .

3


  1. Explanation :

    Let the number be 15x and 15y, where x and y are co –prime. 15x × 15y = 6300

    xy = 6300 = 28

                  15 x 15

    So, two pairs are (7, 4) and (14, 2)

Q.18

The HCF of two numbers is 15 and their LCM is 225. If one of the number is 75, then the other number is

105

90

60

45

Ans .

4


  1. Explanation :

    Using Rule 1, First number × Second number = HCF × LCM 75 × Second number = 15 × 225

    Second number = 15 x 225 = 45


           75

Q.19

The LCM of two numbers is 520 and their HCF is 4. If one of the number is 52, then the other number is

40

42

50

52

Ans .

1


  1. Explanation :

    Using Rule 1, First number × second number = HCF × LCM

    52 × second number = 4 x 520 = 40


           52

Q.20

The H.C.F. of two numbers is 96 and their L.C.M. is 1296. If one of the number i s 864, the other is

132

135

140

144

Ans .

4


  1. Explanation :

    Using Rule 1, First number × Second number = HCF × LCM 864 × Second number = 96 × 1296

    Second number = 96 x 1296 = 144


           864

Q.21

The LCM of two numbers is 4 times their HCF. The sum of LCM and HCF is 125. If one of the number is 100, then the other number is

5

25

100

125

Ans .

2


  1. Explanation :

    Using Rule 1, Let LCM be L and HCF be H, then L = 4H H + 4H = 125 5H = 125

    H = 125 = 25

           5 L = 4 × 25 = 100

    Second number = L x H

           First number

    = 100 x 25 = 25


           100

Q.22

Product of two co-prime numbers is 117. Then their L.C.M. is

117

9

13

39

Ans .

1


  1. Explanation :

    HCF of two-prime numbers = 1 Product of numbers = their LCM = 117

    117 = 13 × 9 where 13 & 9 are co-prime. L.C.M (13,9) = 117.

Q.23

The product of two numbers is 2160 and their HCF is 12. Num- ber of such possible pairs is

1

2

3

4

Ans .

2


  1. Explanation :

    HCF = 12 Numbers = 12x and 12y where x and y are prime to each other. 12x × 12y = 2160

    xy = 2160

           12 x 12

    = 15 = 3 × 5, 1 × 15 Possible pairs = (36, 60) and (12, 180)

Q.24

LCM of two numbers is 2079 and their HCF is 27. If one of the number is 189, the other num- ber is

297

584

189

216

Ans .

1


  1. Explanation :

    Using Rule 1, Second number
    = H.C.F. x L.C.M.        First Number

    = 27 x 2079 = 297


           189

Q.25

The product of two numbers is 2028 and their HCF is 13. The number of such pairs is

1

2

3

4

Ans .

2


  1. Explanation :

    Here, HCF = 13 Let the numbers be 13x and 13y where x and y are Prime to each other. Now, 13x × 13y = 2028

    xy = 2028 = 12

           13 x 13 The possible pairs are : (1, 12), (3, 4), (2, 6) But the 2 and 6 are not co-prime.

    The required no. of pairs = 2

Q.26

The HCF and LCM of two num- bers are 13 and 455 respectively. If one of the number lies between 75 and 125, then, that number is :

78

91

104

117

Ans .

2


  1. Explanation :

    HCF = 13 Let the numbers be 13x and 13y. Where x and y are co-prime. LCM = 13 xy 13 xy = 45

    xy = 455 = 35 = 5 x 7

           13

    Numbers are 13 × 5 = 65 and 13 × 7 = 91

Q.27

The H.C.F. of two numbers is 8. Which one of the following can never be their L.C.M.?

24

48

56

60

Ans .

4


  1. Explanation :

    HCF of two numbers is 8. This means 8 is a factor common to both the numbers. LCM is common multiple for the two numbers, it is divisible by the two numbers. So, the required answer = 60

Q.28

The HCF of two numbers is 23 and the other two factors of their LCM are 13 and 14. The larger of the two numbers is :

276

299

345

322

Ans .

4


  1. Explanation :

    Let the numbers be 23x and 23y where x and y are co-prime. LCM = 23 xy As given, 23xy = 23 × 13 × 14 x = 13, y = 14

    The larger number = 23y = 23 × 14 = 322

Q.29

The L.C.M. of three different num- bers is 120. Which of the follow- ing cannot be their H.C.F.?

8

12

24

35

Ans .

4


  1. Explanation :

    LCM = 2 × 2 × 2 × 3 × 5 Hence, HCF = 4, 8, 12 or 24 According to question 35 cannot be H.C.F. of 120.

Q.30

The H.C.F. and L.C.M. of two numbers are 44 and 264 respec- tively. If the first number is di- vided by 2, the quotient is 44. The other number is

147

528

132

264

Ans .

3


  1. Explanation :

    Using Rule 1, First number = 2 × 44 = 88 First number × Second number = H.C.F. × L.C.M. 88 × Second numebr = 44 × 264

    Second number = 44 x 264 = 13


           88

Q.31

The least number which when divided by 4, 6, 8, 12 and 16 leaves a remainder of 2 in each case is

46

48

50

56

Ans .

3


  1. Explanation :

    Using Rule 4, L.C.M. of 4, 6, 8, 12 and 16 = 48
    Required number = 48 + 2 = 50

Q.32

The least number, which when divided by 12, 15, 20 or 54 leaves a remainder of 4 in each case, is

450

454

540

544

Ans .

4


  1. Explanation :

    Using Rule 4, LCM of 15, 12, 20, 54 = 540
    Then number = 540 + 4 = 544 [4 being remainder]

Q.33

Find the greatest number of five digits which when divided by 3, 5, 8, 12 have 2 as remainder

99999

99958

99960

99962

Ans .

4


  1. Explanation :

    Using Rule 4, The greatest number of five digits is 99999. LCM of 3, 5, 8 and 12
    2   3, 5, 8, 12
    2   3, 5, 4, 6
    3   3, 5, 2, 3
         1, 5, 2, 1 LCM = 2 × 2 × 3 × 5 × 2 = 120 After dividing 99999 by 120, we get 39 as remainder 99999 – 39 = 99960 = (833 × 120) 99960 is the greatest five digit number divisible by the given divisors. In order to get 2 as remainder in each case we will simply add 2 to 99960.

    Greatest number = 99960 + 2 = 99962

Q.34

The least multiple of 13, which on dividing by 4, 5, 6, 7 and 8 leaves remainder 2 in each case is

2520

842

2522

840

Ans .

3


  1. Explanation :

    Using Rule 4, LCM of 4, 5, 6, 7 and 8
    = 2   4, 5, 6, 7, 8
    2   2, 5, 3, 7, 4
         1, 5, 3, 7, 2 = 2 × 2 × 2 × 3 × 5 × 7 = 840. let required number be 840 K + 2 which is multiple of 13. Least value of K for which (840 K + 2) is divisible by 13 is K = 3

    Required number = 840 × 3 + 2 = 2520 + 2 = 2522

Q.35

A, B, C start running at the same time and at the same point in the same direction in a circular sta- dium. A completes a round in 252 seconds, B in 308 seconds and C in 198 seconds. After what time will they meet again at the start- ing point ?

26 minutes 18 seconds

42 minutes 36 seconds

45 minutes

46 minutes 12 seconds

Ans .

4


  1. Explanation :

    Required time = LCM of 252, 308 and 198 seconds
    2   252, 308, 198
    2   126, 154, 99
    7   63, 77, 99
    9   9, 11, 99
    11   1, 11, 11
         1, 1, 1
    LCM = 2 × 2 × 7 × 9 × 11 = 2772 seconds = 46 minutes 12 seconds

Q.36

Find the largest number of four digits such that on dividing by 15, 18, 21 and 24 the remainders are 11, 14, 17 and 20 respectively.

6557

7556

5675

7664

Ans .

2


  1. Explanation :

    15 = 3 × 5
    18 = 32 × 2 21 = 3 × 7

    24 = 23 × 3

    LCM = 8 × 9 × 5 × 7 = 2520 The largest number of four digits = 9999 2520 ) 9999 ( 3

               7560

               2439 Required number = 9999 – 2439 – 4 = 7556 (Because 15 – 11 = 4 18 – 14 = 4 21 – 17 = 4

    24 – 20 = 4)

Q.37

The least perfect square, which is divisible by each of 21, 36 and 66 is

214344

214434

213444

231444

Ans .

3


  1. Explanation :

    LCM of 21, 36 and 66 LCM = 3 × 2 × 7 × 6×11 = 3 × 3 × 2 × 2 × 7 × 11

    Required number = 32 × 22 × 72 × 112 = 213444

Q.38

The least number, which when divided by 4, 5 and 6 leaves re- mainder 1, 2 and 3 respectively, is

57

59

61

63

Ans .

1


  1. Explanation :

    Using Rule 5, Here 4 – 1 = 3, 5 – 2 = 3, 6 – 3 = 3 The required number = LCM of (4, 5, 6) – 3

    = 60 – 3 = 57

Q.39

Let the least number of six dig- its which when divided by 4, 6, 10, 15 leaves in each case same remainder 2 be N. The sum of digits in N is :

3

5

4

6

Ans .

2


  1. Explanation :

    LCM of 4, 6, 10, 15 = 60 Least number of 6 digits = 100000 The least number of 6 digits which is exactly divisible by 60 = 100000 + (60 – 40) = 100020 Required number (N) = 100020 + 2 = 100022 Hence,

    the sum of digits = 1 + 0 + 0 + 0 + 2 + 2 = 5

Q.40

Which is the least number which when doubled will be exactly divisible by 12, 18, 21 and 30 ?

2520

1260

630

196

Ans .

3


  1. Explanation :

    The LCM of 12, 18, 21, 30
    2   12, 18, 21, 30
    3   6, 9, 21, 15
         2, 3, 7, 5 LCM = 2 × 3 × 2 × 3 × 7 × 5 = 1260 The required number

    1260 = 630


       2

Q.41

The smallest square number di- visible by 10, 16 and 24 is

900

1600

2500

3600

Ans .

4


  1. Explanation :

    2   10, 16, 24
    2   5, 8, 12
    2   5, 4, 6
    2   5, 2, 3
    3   5, 1, 3
    5   5, 1, 1
         1, 1, 1
    LCM = 22 × 22 × 3 × 5
    Required number = 2 × 2 × 2 × 2 × 3 × 3 × 5 × 5 = 3600

Q.42

If the students of a class can be grouped exactly into 6 or 8 or 10, then the minimum number of students in the class must be

60

120

180

240

Ans .

2


  1. Explanation :

    Required number of students =
    LCM of 6, 8, 10 = 120

Q.43

The least number which when divided by 4, 6, 8 and 9 leave zero remainder in each case and when divided by 13 leaves a re- mainder of 7 is :

144

72

36

85

Ans .

2


  1. Explanation :

    LCM of 4, 6, 8, 9
    2   4, 6, 8, 9
    3   2, 3, 4, 9
    3   1, 3, 2, 9
         1, 1, 2, 3 LCM = 2 × 2 × 3 × 2 × 3 = 72

    Required number = 72, because it is exactly divisible by 4, 6, 8 and 9 and it leaves remainder 7 when divided by 13

Q.44

The smallest number, which when divided by 12 and 16 leaves remainder 5 and 9 respec- tively, is :

55

41

39

29

Ans .

2


  1. Explanation :

    Using Rule 5, Here, 12 – 5 = 7, 16 – 9 = 7
    Required number = (L.C.M. of 12 and 16) – 7 = 48 – 7 = 41

Q.45

A number which when divided by 10 leaves a remainder of 9, when divided by 9 leaves a remainder of 8, and when divided by 8 leaves a remainder of 7, is :

1539

539

359

1359

Ans .

3

Using Rule Number 5,
  1. Explanation :

    Here, Divisor – remainder = 1 e.g., 10 – 9 = 1, 9 – 8 = 1, 8 – 7 = 1

    Required number = (L.C.M. of 10, 9, 8) –1 = 360 – 1 = 359

Q.46

What is the smallest number which leaves remainder 3 when divided by any of the numbers 5, 6 or 8 but leaves no remain- der when it is divided by 9 ?

123

603

723

243

Ans .

4


  1. Explanation :

    We find LCM of 5, 6 and 8 5=5 6=3×2

    8=23


    = 23×3 × 5 = 8 × 15 = 120 Required number = 120K + 3
    when K = 2, 120 × 2 + 3 = 243 required no. It is completely divisible by 9

Q.47

The least number which when di- vided by 16, 18, 20 and 25 leaves 4 as remainder in each case but when divided by 7 leaves no re- mainder is

17004

18000

18002

18004

Ans .

4


  1. Explanation :

    LCM of 16, 18, 20 and 25 = 3600
    Required number = 3600K + 4 which is exactly divisible by 7 for certain value of K. When K = 5, number = 3600 × 5 + 4 = 18004 which is exactly divisible by 7.

Q.48

What is the least number which when divided by the numbers 3, 5, 6, 8, 10 and 12 leaves in each case a remainder 2 but when di- vided by 13 leaves no remainder ?

312

962

1562

1586

Ans .

2


  1. Explanation :

    LCM of 3, 5, 6, 8, 10 and 12 = 120 Required number = 120x + 2, which is exactly divisible by 13. 120x + 2 = 13 × 9x + 3x + 2 Clearly 3x + 2 should be divisible by 13. For x=8,3x + 2 is divisible by 13.

    Required number = 120x + 2 = 120 × 8 + 2 = 960 + 2 = 962

Q.49

The least multiple of 7, which leaves the remainder 4, when divided by any of 6, 9, 15 and 18, is

76

94

184

364

Ans .

4


  1. Explanation :

    LCM of 6, 9, 15 and 18
    2   6, 9, 15, 18
    3   3, 9, 15, 9
    3   1, 3, 5, 3
         1, 1, 5, 1 LCM = 2 × 3 × 3 × 5 = 90

    Required number = 90k + 4, which must be a multiple of 7 for some value of k. For k = 4, Number = 90 × 4 + 4 = 364, which is exactly divisible by 7.

Q.50

The largest number of five digits which, when divided by 16, 24, 30, or 36 leaves the same re- mainder 10 in each case, is

99279

99370

99269

99350

Ans .

2


  1. Explanation :

    Using Rule 9, We will find the LCM of 16, 24, 30 and 36.
    2   16, 24, 30, 36
    2   8, 12, 15, 18
    2   4, 6, 15, 9
    3   2, 3, 15, 9
         2, 1, 5, 3 LCM = 2 × 2 × 2 × 3 × 2 × 5 × 3 = 720 The largest number of five digits = 99999 On dividing 99999 by 720, the remainder = 639 The largest five-digit number divisible by 720 = 99999 – 639 = 99360

    Required number = 99360 + 10 = 99370

Q.51

The smallest number, which when divided by 5, 10, 12 and 15, leaves remainder 2 in each case; but when divided by 7 leaves no remainder, is

189

182

175

91

Ans .

2


  1. Explanation :

    LCM of 5, 10, 12, 15
    2   5, 10, 12, 15
    3   5, 5, 6, 15
    5   5, 5, 2, 5
         1, 1, 2, 1 LCM = 2 × 3 × 5 × 2 = 60 Number = 60k + 2 Now, the required number should be divisible by 7. Now, 60k + 2 = 7 × 8k + 4k + 2 If we put k = 3, (4k + 2) is equal to 14 which is exactly divisible by 7.

    Required number = 60 × 3 + 2 = 182

Q.52

What least number must be sub- tracted from 1936 so that the resulting number when divided by 9, 10 and 15 will leave in each case the same remainder 7 ?

37

36

39

30

Ans .

3


  1. Explanation :

    LCM of 9, 10 and 15 = 90 Þ The multiple of 90 are also divisible by 9, 10 or 15. 21 × 90 = 1890 will be divisible by them.

    Now, 1897 will be the number that will give remainder 7. 1936 – 1897 Required number = 1936 – 1897 = 39

Q.53

The least number, which when divided by 18, 27 and 36 sepa- rately leaves remainders 5,14, and 23 respectively, is

95

113

149

77

Ans .

1


  1. Explanation :

    The difference between the divisor and the corresponding remainder is same in each case ie. 18 – 5 = 13, 27 – 14 = 13, 36 – 23 = 13
    Required number = (LCM of 18, 27, and 36 ) – 13 = 108 – 13 = 95





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