math
posted by john on .
john takes 3hours longer than andrew to peel 400 pounds of apples. if together they can peel 400pounds of apples in 8hours then how long would it take john if he is working alone.

Andrew's rate = 400/x
Johns rate = 400/(x+3)
combined rate = (400(x+3) + 400x)/(x(x+3)
= 400(2x+2)/(x(x+2))
400 / [400(2x+3)/(x(x+3) ] = 8
1/[2x+3)/(x(x+2)) ] = 8
x(x+3)/(2x+3) = 8
x^2+3x = 16x + 24
x^2  13x  24 = 0
x = (13 ±√265)/2
x = 14.64 hrs , ignoring the negative answer
check:
combined rate = 1/14.64 + 1/17.64 = .125
time at comined time = 1/.125 = 8 , Yeahh!
Andrew alone can do it in 14.65 hrs
John alone can do it in 17.65 hrs