What is the value of integer x?

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What is the value of integer x?

by M7MBA » Sun Oct 29, 2017 7:07 am
What is the value of integer x?

(1) The least common multiple of x and 45 is 225.
(2) The least common multiple of x and 20 is 300.

The OA is C.

I need some help here. How can I use the statements to get the value of x?
Source: — Data Sufficiency |

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by Jay@ManhattanReview » Mon Oct 30, 2017 1:28 am
M7MBA wrote:What is the value of integer x?

(1) The least common multiple of x and 45 is 225.
(2) The least common multiple of x and 20 is 300.

The OA is C.

I need some help here. How can I use the statements to get the value of x?
(1) The least common multiple of x and 45 is 225.

LCM = 225 = 3^2.5^2 and 45 = 3^2.5

x = 3^n.5^2; where n = 0, 1 or 2. No unique answer value of x. Insufficient

(2) The least common multiple of x and 20 is 300.

LCM = 300 = 2^2.3.5^2 and 20 = 2^2.5

x = 2^m.3.5^2; where m = 0, 1 or 2. No unqiue answer. Insufficient

(1) and (2) combined:

From (1) and (2), we get x = 3^n.5^2 = 2^m.3.5^2

=> n = 1 and m = 0

Thus, x = 2^0.3.5^2 = 3.25 = 75. Sufficient

The correct answer: C

Hope this helps!

-Jay

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