susan can paint a chair in 3 hours. jerry can paint in the same size 2.5 hours. working together, how long will it take to paint 10 chairs?

Answer 1

Susan's rate = 1/3
Jerry's rate = 1/2.5
combined rate = 1/3 + 1/2.5 = 11/15

so time taken to do one chair = 1/(11/15) = 15/11

so to do 10 chairs will take 10(15/11) hours
or 13.636 hours. or 13 hours and appr. 38 minutes