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 ÷ 2) | 2 - 3 - 7 - 5
= 630.Discussion:
30 comments Page 1 of 3.
Sanjana said:
6 years ago
Let the number Be N.
Then LCM of 12,18,21,30 is 1260and given that 2N/1260 leaves no remainder.
Now, N/630 this means we have to find the least value of N from options which when divided by 630 leaves no remainder.
Although, options b, c, d leaves no remainder when divided by 630 we had been asked the least value of N, so option 2 i.e., 630 is the answer
Then LCM of 12,18,21,30 is 1260and given that 2N/1260 leaves no remainder.
Now, N/630 this means we have to find the least value of N from options which when divided by 630 leaves no remainder.
Although, options b, c, d leaves no remainder when divided by 630 we had been asked the least value of N, so option 2 i.e., 630 is the answer
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
Madhur Nanhorya said:
10 months ago
Guys just divide each option by 30, so you will see
196/30 ==> r!=0
630/30 ==> r =0,
1260/30 ==> r=0,
2520/30 ==> r = 0, so the least number divisible by 30 is 630 so it must be divisible by other numbers.
As well according to the question,
So option b) 630 no need to find the LCM here.
196/30 ==> r!=0
630/30 ==> r =0,
1260/30 ==> r=0,
2520/30 ==> r = 0, so the least number divisible by 30 is 630 so it must be divisible by other numbers.
As well according to the question,
So option b) 630 no need to find the LCM here.
(3)
Abhilash said:
7 years ago
@Mobin.
The easiest way of finding HCF for eg; 12, 18, 21, 30
Ans : 3.
First, see the least difference between any two numbers, suppose between 18 and 21, the diff is 3.
Now see if 12,18,21,30 are divisible by 3. If divisible then 3 is the answer.
The easiest way of finding HCF for eg; 12, 18, 21, 30
Ans : 3.
First, see the least difference between any two numbers, suppose between 18 and 21, the diff is 3.
Now see if 12,18,21,30 are divisible by 3. If divisible then 3 is the answer.
Krishna said:
2 weeks ago
But 630 is not exactly divisible by 12 it's 52. 5.
@Vradhi.
They asked that the doubled number needs to be divisible by the given number, which means 630 doubled is 1260.
So, it's divisible, then 630 is the answer.
@Vradhi.
They asked that the doubled number needs to be divisible by the given number, which means 630 doubled is 1260.
So, it's divisible, then 630 is the answer.
Yemysle said:
6 years ago
Since the L.C.M is 1260, the question says find the number which when doubled will give exactly as the given number(12,18,21,30) therefore 630 will be doubled to give d LCM(1260) or half if 1260.
(5)
Arun said:
5 years ago
The question itself says that the least number is exactly divisible by (12,18,21,30 ).
The L.C.M of (12,18,21,30) = ( 2*3*2*3*7*5 ) = 1260.
So the least number is 2. 1260÷2.
The L.C.M of (12,18,21,30) = ( 2*3*2*3*7*5 ) = 1260.
So the least number is 2. 1260÷2.
(5)
ASHLY said:
2 years ago
Very simple,
Let the last number be 'x' ;
And given the least number is doubled then it will become '2x'.
Now,
L.C.M of (12,18,21,30) is 1260,
2x = 1260.
x = 630.
THANKS!
Let the last number be 'x' ;
And given the least number is doubled then it will become '2x'.
Now,
L.C.M of (12,18,21,30) is 1260,
2x = 1260.
x = 630.
THANKS!
(70)
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.
Aman said:
4 years ago
Let the least number say x;
And given least number is doubled then it will become =2x;
then,
find lcm (12,18,21,30) we get 1260;
2x = 1260,
x = 630.
And given least number is doubled then it will become =2x;
then,
find lcm (12,18,21,30) we get 1260;
2x = 1260,
x = 630.
(43)
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