Problems on H.C.F and L.C.M
- 1. What least number must be subtracted from 1294 so that the remainder when divided by 9, 11,13 will leave in each case the same remainder 6?
Options- A. 0
- B. 1
- C. 2
- D. 3 Discuss
Correct Answer: 1
Explanation:
The number when divided by 9, 11, 13 leaving remainder 6 = (i.c.m. of 9, 11, 13) + 6 = 1293
Required least number = 1294 - 1293 = 1.
- 2. Find the number lying between 900 and 1000 which when divided by 38 and 57, leaves in each case a remainder 23?
Options- A. 935
- B. 945
- C. 925
- D. 955 Discuss
Correct Answer: 935
Explanation:
The least common multiple of 38 and 57 is 114 and the multiple which is between 900 and 1000 is 912.
Now, 912 + 23 i,e 935 lies between 900 and 1000 and when divided by 38 and 57 leaves in each case 23 as the remainder.
Therefore, 935 is number required.
- 3. Find the sum of three numbers which are prime to one another such that the product of the first two is 437 and that of the last two is 551?
Options- A. 91
- B. 81
- C. 71
- D. 70 Discuss
Correct Answer: 71
Explanation:
From the question we see that the second number is a common factor of the two products and since the numbers are prime to one another. It is their . H. C. F . and is, therefore, 19.
? The first number = 437 / 19 = 23
and the third number = 551 / 19 = 29
Hence, the number are 23, 19 and 29
? Sum = 23 + 19 + 29
= 71.
- 4. What least number must be subtracted from 1936, so that the remainder when divided by 9, 10, 15 will leave in each case the same remainder 7?
Options- A. 46
- B. 53
- C. 39
- D. 44 Discuss
Correct Answer: 39
Explanation:
The L.C.M of 9, 10, 15 = 90
On dividing 1936 by 90, the remainder = 46
But a part of this remainder = 7
Hence, the two numbers = 46 - 7 = 39.
- 5. An inspector of schools wishes to distribute 84 balls and 180 bats equally among a number of boys. Find the greatest number receiving the gift in this ways?
Options- A. 14
- B. 15
- C. 16
- D. 12 Discuss
Correct Answer: 12
Explanation:
Find the H.C.F. of 84 and 180, which is 12 and this is the required answer .
- 6. The greatest possible length which can be used to measure exactly the lengths 7m, 3m 85cm, 12m 95 cm, is?
Options- A. 15 cm
- B. 25 cm
- C. 35 cm
- D. 42 cm Discuss
Correct Answer: 35 cm
Explanation:
Required length = H.C.F of 700, 385, 1295 cm
= 35 cm.
- 7. The sum of two number is 216 and their H.C.F is 27. The numbers are?
Options- A. 54, 162
- B. 108, 108
- C. 27, 189
- D. None of these Discuss
Correct Answer: 27, 189
Explanation:
Let the number be 27a and 27b
Then, 27a + 27b = 216
or a + b = 216/27 = 8
? Values of co-primes with sum 8 are (1, 7) and (3, 5)
So, the number are (27 x 1 , 27 x 7) i.e. (27, 189)
- 8. The product of two-digit numbers is 2160 and their G.C.M is 12. The numbers are?
Options- A. 72, 30
- B. 36, 60
- C. 96, 25
- D. None of these Discuss
Correct Answer: 36, 60
Explanation:
Let the number be 12a and 12b
Then 12a x 12b = 2160
or ab = 15
? Values of co-primes a and b are (1, 15), (3, 5)
So, the two digit number are 12 x 3 and 12 x 5 i.e. 36 and 60 .
- 9. The H.C.F of two number is 16 and their L.CM is 160. If one of the numbers is 32, then the other number is?
Options- A. 48
- B. 80
- C. 96
- D. 112 Discuss
Correct Answer: 80
Explanation:
Product of two numbers = LCM of two numbers x HCF of two numbers.
? N x 32 = 160 x 16
? N = 80
- 10. The product of two numbers is 1600 and their H.C.F is 5. The L.C.M. of the numbers is?
Options- A. 320
- B. 1605
- C. 1595
- D. 8000 Discuss
Correct Answer: 320
Explanation:
Product of two numbers = LCM of two numbers x HCF of two numbers.
? 1600 = LCM x 5
? LCM = 320
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