A librarian was packing some books. She discarded 22 books with torn pages.

She then packed the rest equally into 9 shelves.

There were 11 books on each shelf.

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?