If the circumference of a circle inscribed in a square is 25π, what is the perimeter of the square?

A. 20

B. 25

C. 40

D. 50

E. 100

Correct Answer: E

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You’ll find tons of practice questions, explanations for GMAT Official Guide questions, and strategies on our GMAT Question of the Day page.

## Here are a few other extra challenging GMAT questions with in depth explanations:

Here’s a tough function question from the GMAT Prep tests 1 and 2:

For which of the following functions is f(a+b) = f(b) + f(a) for all positive numbers a and b?

And a very challenging word problem from the Official Guide. Almost no-one gets this one on the first try but there is a somewhat simple way through it:

Tanya’s letters from the GMAT Prep tests. This one often gets GMAT tutoring students caught up in a tangled net. With combinatorics it’s important to stay practical. We’ll take a look at how to do that in the explanation:

Here’s an exponents puzzle that comes up a lot in GMAT tutoring sessions:

This is one of the most difficult questions in the GMAT universe. That said, there is a simple way to solve it that relies on a fundamental divisibility rule every GMAT studier should know:

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