SOLUTION: Togethe, John and Mark can finish painting a house in 10 hours. Alone, John takes 4 hours longer than Mark to finish painting the same house. How long does Mark take to finish pain

Algebra ->  Quadratic Equations and Parabolas -> SOLUTION: Togethe, John and Mark can finish painting a house in 10 hours. Alone, John takes 4 hours longer than Mark to finish painting the same house. How long does Mark take to finish pain      Log On


   

Question 133431: Togethe, John and Mark can finish painting a house in 10 hours. Alone, John takes 4 hours longer than Mark to finish painting the same house. How long does Mark take to finish painting the house by himself?. Give your correct answer to correct 2 decimal places.



Answer by scott8148(6628) About Me  (Show Source):
You can put this solution on YOUR website!
let x="Mark's time", so x+4="John's time"

10%2Fx%2B10%2F%28x%2B4%29=1 __ multiplying by x(x+4) __ 10x+40+10x=x^2+4x

subtracting 20x+40 __ 0=x^2-16x-40

use quadratic formula to find x