Question

Diana can check 25 english papers in 2 hours. When Frankie helps, they can do the job together in 30 minutes. How long would it have taken Frankie to grade 25 English papers by himself ?

Answer 1

25 papers = (25 / 2)(1 / 2)+(x / hours)(1 / 2)
25 papers = (25 / 4)+(x / 2)
100 = 25 + 2x
100 - 25 = 75       x=75/2 pages per hour
(2 / 75)(25 = (2 / 3) = 40 minutes