The diagram shows a square ABCD. D
N
bu
A
M
I
Mis the midpoint of AB.
Nis the midpoint of AD.
The area of the shaded triangle AMN is 18 cm
Work out the area of triangle MCN.

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?