Working alone, bill can paint a house in 4 hours. when tom , the job takes 2.5 hours. if tom worked alone, how long would it take him to paint the house ?

Bill's rate is 1 house / 4 hours = 1/4 house per hour.

Tom's rate is

Bill and Tom's combined rate  satisfies

 







So it takes Tom  hour (6 hours 40 minutes) to paint a house

Check:

[/tex]3/20 + 1/4 =3/20 + 5/20 = 8/20 quad[/tex] 8 houses per twenty hours, 2.5 hours per house