Steve saw 313 birds during a bird-watching trip to Yellowstone National park. He observes 15 more trumpeter swans than sandhill cranes. He saw twice as many mountain chickadees as ducky grouses. How many birds of each type did steve observe if he saw half as many trumpeter swans than ducky grouses?

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?