Question

Team X can set up chairs in the gym in 15 minutes and team Y can set up the chairs in 20 minutes. How much time would they take, working together, to set up the same chairs?

Answer 1

Team X : 1min --> 1/15 chairs
Team Y : 1min --> 1/20 chairs
Team X&Y : 1min --> 1/15 + 1/20 = 7/60 chairs
X min --> 60/60 chairs
X= 60/7 min