math
posted by Dennis on .
cory drops a bouncing ball form a height of 50 ft and it rebounds to 90% of its previous height.find the total distance the ball will have travelled when it hits the ground for the fifth time

50 + .9 * 2 * 50 + .9^2*2*50 +.9^3*2*50 +.9^4 *2 * 50
= 50 +100 + 100 (.9^1 +.9^2 + .9^3 + .9^4)
50 + geometric series g=100 n = 5, r = .9 in
Sum5 = 100(1.9^4)/(1.9)
= 100 (.3439)/.1 = 344
50 + 344 = 294 
An apple farmer went to town to sell a truck full of apples. At his first stop, he sold 1/3 of his apples. On the way to the next stop, he wrecked his truck and lost 1/3 of the remaining apples. Of those left, the farmer gave away 1/2 to some children. He then has 80 apples left. How many apples did the farmer have when he started his trip?