Daria can wash 3 cars in 2 hours Larry can wash the same 3 cars in 1.5 hours how long will it take to wash the 3 cars if they work together?

Answer 1

This is a rate equation:

(Rate Daria) times t plus (Rate Larry) times tequals number of cars to wash

Daria's rate is 3/120 and Larry's rate is 3/90

(3/120) x t + (3/90) x t = 3 (three cars to wash, this could be any number of cars to wash)

t x ((3/120) + (3/90)) = 3, multiply both sides by 120, 360/90 = 4 give:

t x (3+4) = 360

t = 360/7 = 51.42857 minutes which is about 51 minutes