Atriangle-shaped machine part has sides of 21/2 inches, 31/4 inches, and 5 inches. the triangle's perimeter is
a. 103/4 inches.
b. 111/2 inches.
c. 113/8 inches.
d. 101/8 inches.

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?