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If a and b are positive integers, what is the units digit of

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If a and b are positive integers, what is the units digit of [#permalink] New post 17 Jun 2014, 11:28
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If a and b are positive integers, what is the units digit of b ?

(1) b is 25% greater than a.

(2) If b is decreased by 50%, the result is not an integer.
[Reveal] Spoiler: OA

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Last edited by Bunuel on 17 Jun 2014, 11:32, edited 1 time in total.
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Re: If a and b are positive integers, what is the units digit of [#permalink] New post 17 Jun 2014, 11:36
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If a and b are positive integers, what is the units digit of b ?

(1) b is 25% greater than a --> b=1.25a --> b/a = 5/4 --> b is a multiple of 5. So, the units digit of b could be 0 as well as 5. Not sufficient.

(2) If b is decreased by 50%, the result is not an integer --> b/2 is not an integer --> b is not even. Not sufficient.

(1)+(2) Since b is not even, then its units digit cannot be 0, thus from (1) its units digit must be 5. Sufficient.

Answer: C.

Hope it's clear.
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Re: If a and b are positive integers, what is the units digit of [#permalink] New post 18 Jun 2014, 06:14
dont recollect seeing this question in OG ..
Re: If a and b are positive integers, what is the units digit of   [#permalink] 18 Jun 2014, 06:14
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