# tim washes cars three times slower than bill

by Maria
(Los Angeles, CA, USA)

tim washes cars three times slower than bill if they both wash 9 cars in one hour how long does it take bill to wash a car

### Comments for tim washes cars three times slower than bill

 Jul 01, 2011 Work-Rate Problem by: Staff The question: by Maria (Los Angeles, CA, USA) tim washes cars three times slower than bill if they both wash 9 cars in one hour how long does it take bill to wash a car The answer: Variables: x = cars washed by Tim each hour = unknown y = cars washed by Bill each hour = unknown t = time in hours = 1 c = cars washed = 9 general equation x*t + y*t = c Tim washes cars three times slower than Bill (it takes Tim three times as much time as it takes Bill) x = y/3 substitute all known values into the general equation x*t + y*t = c (y/3)*1 + y*1 = 9 Solve for y (y/3)*1 + y*1 = 9 (y/3) + y = 9 Multiply each side of the equation by 3 (y/3) + y = 9 3*(y/3) + 3*y = 3*9 y*(3/3) + 3*y = 3*9 y*(1) + 3*y = 3*9 y + 3*y = 3*9 y + 3y = 3*9 y + 3y = 27 combine like terms y + 3y = 27 4y = 27 divide each side of the equation by 4 4y = 27 4y/4 = 27/4 y*(4/4) = 27/4 y*(1) = 27/4 y = 27/4 y = 6.75 Bill washes 6.75 cars per hour Time for Bill to wash 1 car = (60 minutes per hour)/(6.75 cars per hour) Time for Bill to wash 1 car = (60 minutes/6.75 cars)*(per hour)/(per hour) Notice that the units “per hour” cancel, leaving only minutes in the final answer Time for Bill to wash 1 car = (60 minutes/6.75 cars)*(1) Time for Bill to wash 1 car = (60 minutes/6.75 cars) Time for Bill to wash 1 car = 8.88889 minutes (about 8 minutes and 53 seconds) The final answer is: Time for Bill to wash 1 car = 8.88889 minutes (about 8 minutes and 53 seconds) Thanks for writing. Staff www.solving-math-problems.com