Question

Maria can clean the entire house in two hours. Her sister, Sasha, can clean the house in three hours. How long would it take for two of them to do the job together?

Answer 1

Maria do 1/2 work in 1 hour
Sasha do 1/3 work in 1 hour

Thus,
1/2+1/3=5/6 work in 1 hour
5/6 work in = 1 hour
1 work in =6/5=1.2 hours =72 minutes