Cubes - GMAT Quantitative

Card 1 of 312

0
Didn't Know
Knew It
0
1 of 2019 left
Question

What is the length of the diagonal of a cube if its side length is ?

Tap to reveal answer

Answer

The diagonal of a cube extends from one of its corners diagonally through the cube to the opposite corner, so it can be thought of as the hypotenuse of a right triangle formed by the height of the cube and the diagonal of its base. First we must find the diagonal of the base, which will be the same as the diagonal of any face of the cube, by applying the Pythagorean theorem:

Now that we know the length of the diagonal of any face on the cube, we can use the Pythagorean theorem again with this length and the height of the cube, whose hypotenuse is the length of the diagonal for the cube:

← Didn't Know|Knew It →