It takes Ben 10 hours to paint the room. Sam can paint the same room in 6 hours. How long would it take for both Ben and Sam to oil the lanes, if they work together?

Answer 1

1/10 + 1/6 = 1/x

multiply by 30

3x+ 5x = 30

8x =30

x = 30/8 = 3.75 hours working together

or

1/10 + 1/6 = 1/x

3/30 + 5/30 = 1/x

8/30 = 1/x

4/15 = 1/x

cross multiply

4x = 15

divide by 4

x = 15/4 = 3 3/4 = 3.75 hours working together