A fill pipe can fill 1/2 of cistern in 20 minutes. In how many minutes, it can fill 1/2 of the cistern?
Choose the correct answer
A) 5 min B) 10 min C) 15 min D) 20 min E) 25 min

Rationale: required time = 20 * 2 * 1 / 2 = 20 minutes answer is d
Answer: D