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

1 Answer
Lucy
May 27, 2018

42 minutes

Explanation:

Scott can do 630 dishes in 105 minutes. Therefore he would wash #630/105# dishes in 1 minute

Joe can do 630 dishes in 70 minutes. Therefore, he would wash #630/70# dishes in 1 minute.

That means that if they wash the dishes together, every minute would mean that they would be able to wash #630/105+630/70=15# dishes in 1 minute.

Since there are 630 dishes to be washed, they would take together
#630/15=42# minutes

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