A can copy 75 pages in 25 hours. A and B together can copy 135 pages in 27 hours. In what time can B copy 42 pages?
Correct Answer: 21 hours
Explanation:
In 25 hours A can copy 75 pages
In 1 hour A can copy 75/25 = 3 pages
In 25 hours (A and B) can copy = 135/27 = 5 pages
∴ In 1 hour B can copy (5 - 3) = 2 pages
∴ B can copy 42 pages in 21 hours.
