Is the integer x a multiple of 10?

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Is the integer x a multiple of 10?

by swerve » Thu Aug 02, 2018 11:08 am

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Source: GMAT Paper Test

Is the integer x a multiple of 10?

(1) When x is divided by 5, the result an even integer.
(2) x + 20 is a multiple of 10.

The OA is D.

Statement 2 : x + 20 can be 10, 20, 30, 40...
So x can be -10, 0, 10, 20, 30...

Can we say that -10 and 0 are also multiples of 10? or just my reasoning above is incorrect?

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by Brent@GMATPrepNow » Thu Aug 02, 2018 3:10 pm

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swerve wrote:Source: GMAT Paper Test

Is the integer x a multiple of 10?

(1) When x is divided by 5, the result an even integer.
(2) x + 20 is a multiple of 10.

The OA is D.

Statement 2 : x + 20 can be 10, 20, 30, 40...
So x can be -10, 0, 10, 20, 30...

Can we say that -10 and 0 are also multiples of 10? or just my reasoning above is incorrect?
Yes, -10 and 0 are multiples of 10.
We say that N is a multiple of d if we can write N = kd, where k is an integer.
So, for example, 24 is a multiple of 8 because we can write 24 = (3)(8), and 3 is an integer.
Likewise, -10 is a multiple of 10 because we can write -10 = (-1)(10), and -1 is an integer.
Similarly, 0 is a multiple of 10 because we can write 0 = (0)(10), and 0 is an integer.

Cheers,
Brent
Brent Hanneson - Creator of GMATPrepNow.com
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