If a ball is rolling down a hill, it has both kinetic and potential energy. The ball has 38 J of potential energy because of its height and 80J of kinetic energy because
of its motion. How much mechanical energy does the ball have

The answer is 118 J :)

Explanation:

38 +80 = 118.

the old price per ounce is c/4.

the new price per ounce is c/3.6.

the ratio of the old price to the new one is

(c/4)/(c/3.6) = (c/c)×(3.6/4) = 0.9 . . = 9/10 . . "nine tenths" in either form