It takes Brian 15 hours longer to build a model car than it takes John. If they work together, they can build the model car in 4 hours. Using complete sentences, explain each step in figuring out how to determine the time it would take Brian to build the car on his own.

Question

directrix · Answer

I'm looking at this approach: http://www.purplemath.com/modules/workprob.htm

anonymous · Answer

Sorry, LaTex/sigma Equation is not working at this time.

1/x + 1/(x + 15) = 1/4
1 car per x hours + 1 car per (x+15) hours equals 1 car in 4 hours.
Solve for x.
x = 5
Brian takes 5 + 15 = 20 hours