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:
30 comments Page 1 of 3.
Saras said:
1 decade ago
why we are dividing by 2?? pl tel me and also tel me some easy tricks for h c m and l c m
Aparna said:
1 decade 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
Priz said:
1 decade ago
Thanks Aparna, it is really helpful
Grishma said:
1 decade ago
How 1260/2 comes?
Deepak said:
1 decade ago
1260/2 come ,because in Q it ask to find least no.(630) which when double to divisible by given no.(12,18,21,30)
Akshara said:
1 decade ago
Double in actual means x*x i.e x^2. The question is perceived as x*2.
Shreya said:
1 decade ago
Because it is already considered as it is doubled in the question that means the lcm is the doubled digit, therefore we divide it by 2 so as to get the least number.
Aadhithyaa said:
1 decade ago
They have told that the required number= (1260/2) = 630, where did that to which divides 1260 come from?
Teja said:
10 years ago
Here, they have given number "which when doubled ", which mean 1260 /2 = 630.
Appalaraju said:
10 years ago
Because it is already considered as it doubled in question only so please read questions and ask your doubts 630 is right answer.
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