What is the remainder when integer n is divided by 10?

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BTGModeratorVI wrote:
Mon Jun 08, 2020 12:02 pm
What is the remainder when integer n is divided by 10?

(1) When n is divided by 110 the remainder is 75.
(2) When n is divided by 100 the remainder is 25.

Answer: D
Source: Princeton Review
Target question: What is the remainder when integer n is divided by 10?

REPHRASED target question: What is the UNITS DIGIT of n?

Statement 1: When n is divided by 110 the remainder is 75.
In other words: n = 110k + 75 (for some integer k)
Since 110k will have units digit 0 for ANY integer k, we know that 110k + 75 MUST have a units digit of 5
In other words, n MUST have a units digit of 5
Since we can answer the REPHRASED target question with certainty, statement 1 is SUFFICIENT

Statement 2: When n is divided by 100 the remainder is 25
In other words: n = 100k + 25 (for some integer k)
Since 100k will have units digit 0 for ANY integer k, we know that 100k + 25 MUST have a units digit of 5
In other words, n MUST have a units digit of 5
Since we can answer the REPHRASED target question with certainty, statement 2 is SUFFICIENT

Answer: D

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Brent
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