when The remainder when 40 is divided by a is 40?

Question

Hi guys, I run in to this data sufficient question in Advanced Quant Mahattan:
2. If a is a positive integer and 81 divided by a results in a remainder of 1, what is the value of a?
(1) The remainder when a is divided by 40 is 0.
(2) The remainder when 40 is divided by a is 40.

But I don't get the statement (2). How can it possible? 
In they solution, they say that: 
"40/a, remainder = 40 => a must be larger than 40". But I don't remember this knowledge indeed. Can anyone help to refer to something we learnt in school related to this?
Thank a lots!

chetan2u · Answer

A number x is the remainder when the divisor > x.

Say, we are dividing 40 by 41.....

Dividend = Divisor × Quotient + Remainder
40=41*0+40
OR
40=80*0+40

Remainder will be the dividend itself

EMPOWERgmatRichC · Answer

Hi hazelvu1010, A discussion of this question can be found here: https://gmatclub.com/forum/if-a-is-a-po ... 34565.html GMAT assassins aren't born, they're made, Rich

LamboWalker · Answer

Helpful tip - Can't find an answer to a GMAT question, or is the explanation hard to understand? Just Google the question. It will most likely be posted on one of the GMAT forums with arguably better explanations than the ones in the books.

ReedArnoldMPREP · Answer

Whenever you divide a number by a larger number, the remainder is just the number you're dividing.

That is: 4/11 has remainder 4 (it's 0 remainder 4). 40/150 is 0 remainder 40. 1/2 is 0 remainder 1.

So if 40/a has remainder 40 means a > 40.

Since 81/a has remainder 1, that means 81 is 1 more than a multiple of a.

Well, 81 is one more than 80, so 80 is a multiple of a (that isn't 1). So a is: 80, 40, 20, 16, 10, 8, 5, 4, or 2.

If a > 40, a must be 80.

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when The remainder when 40 is divided by a is 40?

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