Question

Ian and Nadya can each wash a car and clean its interior in about 2 hours, but Chris needs 3 hours to do the work. If the three work together, how long will it take to clean 7 cars?

Answer 1

My thought is that if it takes one person 3 hrs and it take 2 people 2 hrs, wouldn't it take 3 people one hour to wash a car. Therefore if three people work together it will take an hour for each car resulting in 7 hours for 7 cars.

Answer 2

That was my thought. However, I have the answer to the problem (from the back of the book) and it is 5 hours and 15 minutes. I don't see how this is logical at all but I'd love to figure out how to do it.

Answer 3

Figured it out! If you calculate, it takes Nadya and Ian 1/2 a car an hour and chris cam wash 1/3 a car in an hour. 7 divided by 1 and 1/3 is 5 and 1/4, aka, 5 hours and 15 minutes. YES!

Answer 4

Good Job!