8/25 + 1/2 = ? ? simplify answer fully

The two square pyramids are similar. find the total volume of both pyramids if the ratio of their surface areas is 9/16

Combine like terms to make a simpler expression 3z+z

You are standing next to a really big circular lake. you want to measure the diameter of the lake, but you don't want to have to swim across with a measuring tape! you decide to walk around the perimeter of the lake and measure its circumference, and find that it's 400\pi\text{ m}400? m. what is the diameter dd of the lake?