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by GMATGuruNY » Wed Nov 01, 2017 11:02 am
LUANDATO wrote:If x must be divisible by both 4 and 10, then x must also be divisible by which of the following numbers?

A. 8
B. 20
C. 40
D. 50
E. 80
Let x = the least common multiple of 4 and 10 = 20.
Since x=20 is not divisible by 8, 40, 50, or 80, eliminate A, C, D and E.

The correct answer is B.
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by EconomistGMATTutor » Fri Nov 03, 2017 3:15 pm
If x must be divisible by both 4 and 10, then x must also be divisible by which of the following numbers?

A. 8
B. 20
C. 40
D. 50
E. 80

The OA is B.

I don't understand this PS question. Please, can any expert assist me with it? Thanks.
Hi LUANDATO,
Let's take a look at your question.

The number that is divisible by both 4 and 10 must the least common multiple of both.
Let's first find LCM of 4 and 10.

Multiples of 4 = 4, 8, 12, 16, 20, ...
Multiples of 10 = 10, 20, 30, 40, ...
LCM = 20

Now 20 is divisible by both 4 and 10.
We need to check that which of the given options is divisible by 20.

OPTION A:
8 is not divisible by 20. So Option A is not correct.

OPTION B:
20 is divisible by 20.
Therefore, Option B is correct.

Hope it helps.
I am available if you'd like any follow up.
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by Scott@TargetTestPrep » Thu Oct 31, 2019 5:24 pm
BTGmoderatorLU wrote:If x must be divisible by both 4 and 10, then x must also be divisible by which of the following numbers?

A. 8
B. 20
C. 40
D. 50
E. 80

The OA is B.

I don't understand this PS question. Please, can any expert assist me with it? Thanks.
If a number is divisible by a and b, then it's also divisible by the LCM of a and b. Therefore, since the LCM of 4 and 10 is 20, then x must be divisible by 20.

Answer: B

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