4 men can check exam papers in 8 days working 5 hours regularly. What is the total hours when 2 men will check the double of the papers in 20 days?  Choices
A) 8 B) 9 C) 6 D) 1 E) 5

Rationale: let a man can do 1 unit of work in 1 hour . total units of work = 4 x 8 x 5 = 160 units . now work = 2 x 160 = 320 units . now 2 men work for 20 days . let in x hours they have to work per day . now total work = 2 × x × 20 = 40 x 40 x = 320 so x = 320 / 40 = 8 hours . answer : a
Answer: A