A rectangle has a diagonal of 15cm and a width of 9cm. Find its length. Hint: draw a rectangle and divide in half using a diagonal!

12

Step-by-step explanation:

Imagine a rectangle cut in half along a diagonal. This makes a right angled triangle. This means we can use pythagoras' theorem of a^2+b^2=c^2

For length x we have x^2 + 9^2 = 15^2 so x^2 + 81 = 225

x^2 = 225 - 81 = 144 so x = √144 = 12