Question

Rob can tar a roof in nine hours.One day his friend Kayla helped him and it only took hime 4.74 hours. How long would it take Kayla to do it alone

Answer 1

9x10.014084507 / 9 + 10.014084507 = 4.74
 90.126760563 / 19.014084507= 4.74 4.74 = 4.74

therefore  Kayla can do it in 10.01 hrs