HCF and LCM Quiz Set 002

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Question 1

Three lights are flashing at regular intervals. They, respectively, flash after 18, 36 and 54 seconds. How many times do they together flash in 1836 seconds?

 A

18 times.

 B

19 times.

 C

17 times.

 D

20 times.

Soln.
Ans: a

They will together flash after the LCM of their times. The LCM of 18, 36 and 54 = 108. So they will flash 1 + $1836/108$ = 18 times.


Question 2

Which is the least number which must be added to 4196 so that it becomes divisible by 24, 50 and 105?

 A

4.

 B

5.

 C

3.

 D

6.

Soln.
Ans: a

The LCM of 24, 50 and 105 = 4200. The lcm when divided by either of these numbers leaves the remainder 0. The minimum number to be added is 4200 - 4196 = 4.


Question 3

What is the LCM of ${6/13}$, $3{3/5}$ and ${2/9}$?

 A

18.

 B

19.

 C

20.

 D

21.

Soln.
Ans: a

The LCM of numerators 6, 18 and 2 is 18. The HCF of denominators 13, 5 and 9 is 1. So the required LCM of the given fractions is 18/1 = 18.


Question 4

Which is the smallest number which when divided by 15, 9 or 16 leaves 9, 3, 10 as the respective remainders?

 A

714.

 B

715.

 C

713.

 D

716.

Soln.
Ans: a

By inspection, the difference between the numbers and their respective remainders is same = 6. The LCM of 15, 9 and 16 = 720. So the required number is 720 - 6 = 714.


Question 5

The HCF of two numbers is 7. The factors of their LCM are 7, 13 and 5. Which is the greater of the two numbers?

 A

91.

 B

182.

 C

45.

 D

273.

Soln.
Ans: a

The numbers are 7 × 13 = 91, and 7 × 5 = 35. The greater of them is 91.


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This Blog Post/Article "HCF and LCM Quiz Set 002" by Parveen (Hoven) is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License.
Updated on 2017-06-24.

Posted by Parveen(Hoven),
Aptitude Trainer


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