Question

Help me Please!!!
Richard can paint a room in two hours and his brother Nick can paint the same room in four hours. How long would it take them to paint the room if they worked together?

Answer 1

let t equal their combined time

each one does some fraction of the job
... t / 2 for Richard
... t / 4 for Nick

they combine to do the whole job ... t/2 + t/4 = 1

2t / 4 + t / 4 = 1 ... 3 t = 4 ... t = 4 /3 ... an hour and 20 minutes

Answer 2

1/2 + 1/4 = 1/t
t = 4/3