usre123 wrote:

Thankyou for taking the time to answer, but I dont understand. Why is the side 3?

And why have you added 1+1+3?

Also, as I explained in the pm, we got a handout of these in our gmat class, and the questions just had one single answer. So I dont have the five answer choices.

The inner cube has an area of 27, we know that the area of a coube is \(side^3\) so in this case \(s^3=27\) so \(s=3\)

The inner cube has a side of 3. Good!

Moving on... This is an inner cube, so is contained in a larger cube. The larger cube must

contain the inner cube, and this is possible only if the larger cube has at the end of each side one more cube (look at the image: it's in 2D but the concept is the same)

So we add 1 cube to each side 1+3+1=5, the larger cube has a side of 5 => \(area=5^3=125\)

Hope it's clear now, let me know

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