Data Sufficiency - Digits Problem

[jessy.lacy]

Can anyone explain why the answer is A? Please help...

The product of the units digit, the tens digit, and the hundreds digit of the positive integer m is 96. What is the units digit of m?
(1) m is odd.
(2) The hundreds digit of m is 8.

I answered C and feel that the answer given is wrong. Doubt the correctness of this test:
http://www.exampep.com/gmat/gmat-practice-test-3-quantitative/

[editor: did you find this problem on a practice test at that address?
if so, this question has been stolen, verbatim, from the gmat prep software -- a situation in which gmac would surely be interested.]

[ruchi3d]

The answer A is right.

Ideally in this type of questions, first find all the factors of the number. In this case, 96 has following factors - 2*2*2*2*2*3.

Statement 1 says that unit digit is odd. Only factor which is odd is 3 so this statement is sufficient.

Statement 2 says that hundred digit is 8. But we are not sure of unit digit, it can be 3 or 4.

So answer is 'A'

Thanks,
Ruchi Verma

[jessy.lacy]

Thank you very much for the explanation Ruchi :)

The answer A is right.

Ideally in this type of questions, first find all the factors of the number. In this case, 96 has following factors - 2*2*2*2*2*3.

Statement 1 says that unit digit is odd. Only factor which is odd is 3 so this statement is sufficient.

Statement 2 says that hundred digit is 8. But we are not sure of unit digit, it can be 3 or 4.

So answer is 'A'

Thanks,
Ruchi Verma

[mschwrtz]

Nice job Ruchi.


By the way, the S2 just tells us that between the tens and units digits we have the factors 2, 2, 3, and of course that neither digit is 0. So S2 allow a couple more options than you realized:

826
834
843
862

[rockrock]

which section of the MGMAT books go through units digits properties with problems like this one?

[RonPurewal]

which section of the MGMAT books go through units digits properties with problems like this one?

digit properties are generally in the FDP book.

however, digits have a very strong overlap with remainders -- in fact, "units digit" and "remainder upon division by 10" are exactly the same thing -- so a lot of the material in the Remainders section of the number properties book may also be relevant here.

[rockrock]

ok thanks. that woudl be the remainders advanced section of the NP book then.... Part 1 simply defines what a remainder is!

[mschwrtz]

Well, gotta start somewhere.