Plz, help me with this question!

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?

Awindow washer cleans 42 windows in 2 hours. at this rate, how many windows did he clean in 180 minutes.

Andres wants to share 1/2 of his birthday cake with his friends. if he has 8 friends, how much of the cake will each friend recieve? draw a model to support your work (its ok if you cant)