Jim is standing beside apool. He drops a weight from 4 feet above the surface of the water pool. The weight travels a total distance of 12 feet down before landing on the bottom of the pool. Explain how you can write a sum of integers to find the depth of water.

Treat the surface of the water as 0. The initial height of the weight was 4 ft above the surface of the water, therefore making it have an initial height of + 4. If it travels 12 ft downward to hit the bottom of the pool, that means its height decreased by 12, so its falling is - 12. To calculate the depth of the pool, use initial height minus drop distance, so 4 - 12. The depth of the pool is 8 ft.