Find the length of this face.

Question

A suit case is shaped like a rectangular prism. The length of the diagonal of one of its largest faces is 30 centimeter. The width of this face is 18 centimeter. Find the length of this face.

Answer 1

Hi Desi,

 

I will start by saying that it is difficult to answer geometry questions without drawing so part of the success of my explanation depends on your ability to be able to picture this yourself. I strongly encourage you to draw this and track my answer for it to make sense.

 

Here we go...

 

The largest face diagonal is 30 cm and its width is 18 cm. So the diagonal is also the hypotenuse of the right triangle on this face. We will call the length, l. According to the Pythagorean theorem

30^2 = 18^2 + l^2

l = 24 cm

 

Answer 2

Think of this as a right triangle, where the hypotenuse is the 30 and the shorter leg is 18. Can you use the Pythagorean theorem from there?