Answer to GMAT Question #7

Here is the answer to GMAT Practice Question #7.

Answer: E

Explanation: The way to work out this problem is through algebraic manipulation. Start by plugging 9c into a:

See Figure 1

If you pull out the square root of 9 and turn it into a 3 you can make a new equation that is easier to work with. The new equation will look like this:

See Figure 2

See Figure 3

Now work through the exponents. Since this is all multiplication, you can clear out the exponents by cubing both sides (it would be MUCH tougher if there was any addition or subtraction here):

27(2b) = (2d)

The question asks for b in terms of d, so now just manipulate: d/27

Of course, the answers aren’t written like this. But 27 is the same as 3 to the 3rd power, so the right answer is E.

The answer and explanation to GMAT Practice Question #7 was written by Integrated Learning, a company that provides professional and private one on one tutoring services.