Question

There are 630 dishes that need to be rinsed. boris can rinse them in 105 minutes by himself. it will take his friend reuben 70 minutes to rinse these dishes. how long will it take them if they rinse these 630 dishes together?

Answer 1

Boris:

105 mins = 630 dishes

1 min = 630 ÷ 105 = 6 dishes

Reuben:

70 mins 630 dishes

1 min = 630 ÷ 70 = 9 dishes

Boris and Reuben:

1 min = 6 + 9 = 15 dishes

Number of numbers needed to rinse 630 dishes:

630 ÷ 15 = 42 mins

Answer: They will take 42 mins if they rinse the 630 dishes together.