Aptitude - Problems on H.C.F and L.C.M - Discussion
Discussion Forum : Problems on H.C.F and L.C.M - General Questions (Q.No. 17)
17.
What will be the least number which when doubled will be exactly divisible by 12, 18, 21 and 30 ?
Answer: Option
Explanation:
L.C.M. of 12, 18, 21 30 2 | 12 - 18 - 21 - 30
----------------------------= 2 x 3 x 2 x 3 x 7 x 5 = 1260. 3 | 6 - 9 - 21 - 15
----------------------------Required number = (1260 รท 2) | 2 - 3 - 7 - 5
= 630.Discussion:
31 comments Page 4 of 4.
Aparna said:
2 decades ago
pls remember
whenever dividend is unknown,it is an LCM question
so firstly find the LCM of 12,18,21,30
we get 1260,and this is exactly divisible by 12,18,21,30
as we have asked after doubling the number,it is exactly divisible by the given numbers.
so,1260/2 is done,we get 630
and 630*2=1260,which is asked to us
whenever dividend is unknown,it is an LCM question
so firstly find the LCM of 12,18,21,30
we get 1260,and this is exactly divisible by 12,18,21,30
as we have asked after doubling the number,it is exactly divisible by the given numbers.
so,1260/2 is done,we get 630
and 630*2=1260,which is asked to us
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