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Karen Schweitzer

Can You Solve This GMAT Brain Teaser?

By May 5, 2008

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We are now in our second week of the GMAT challenge. Once again, Intergrated Learning has provided us with another great practice GMAT question.

See if you can answer it:

GMAT Practice Question 2

Q is a two digit number. If 7 is the tens digit of q, what is the units digit of q to the 4th?

1) q is an even integer.
2) q is not a multiple of 5.

A) Statement (1) ALONE is sufficient, but statement (2) is not sufficient.
B) Statement (2) ALONE is sufficient, but statement (1) is not sufficient.
C) BOTH statements TOGETHER are sufficient, but NEITHER statement ALONE is sufficient.
D) EACH statement ALONE is sufficient.
E) Statements (1) and (2) TOGETHER are NOT sufficient.

So, what do you think? Is the answer A, B, C, D or E? You can post you guess in the comments (see below) or discuss the question in the Business School Community Forum.

Don't forget to check back tomorrow for the answer!

To see more GMAT challenges, visit the Integrated Learning Blog.

Comments

May 5, 2008 at 2:28 pm
(1) Gopikrishna C says:

The answer for practice question 2 is C.

May 5, 2008 at 6:29 pm
(2) Tom Steele says:

C. Because 72,74,76 and 78 raised to the fourth power all end with ’6′ as the units digit.

However, 70 must be excluded, so the statement that it cannot be a multiple of 5 must be part of the information given, and;

71 must be excluded so the statement that Q is an even number is required.

May 5, 2008 at 10:32 pm
(3) Bschoolstudent says:

My guess is C too.

May 14, 2008 at 3:57 pm
(4) mona says:

my guess is c.

August 31, 2009 at 4:25 pm
(5) Rick says:

It’s E.

The second poster correctly states that there are four numbers that end in a 6 when raised to the fourth power. There’s also 70, which ends in another even digit (0). So that’s five numbers that end in an even integer.

So there are five numbers that Q can be according to 1). According 2), it can be any of the numbers that aren’t 70 or 75.

If we combine 1) and 2), we are still left with *four* numbers – all the ones that end in 6.

So 1) and 2) does not provide us with an answer, as we can square 72, 74, 76, and 78 and have it still meet both conditions.

October 20, 2009 at 3:08 pm
(6) Stephen says:

You’re right Rick except the question asks: “what is the units digit of q to the 4th?”, not what is Q.

So the units digit of q to the 4th will always be 6 based on 1 and 2 together, so C.

January 20, 2010 at 9:56 pm
(7) AJ says:

whats does it mean by “what is the units digit of q to the 4th?”.. I’m not clear.

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