PLEASE HELP :'(
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?

Question

anonymous · Answer

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!

anonymous · Answer

1/2 +1/2 + 1/3 =4/3
just reverse the answer that is for one car-> 3/4.
multiply with 7 for 7 cars-> 21/4 
so 21/4 hr-> 5hr 15 minutes