Question

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

Answer 1

`\text {Time needed = } (105 * 70)/(105 + 70) = (7350)/(175) = 42 \text { mins}`

Answer: They will need 42 minutes if they work together.