A fill pipe can fill 1/2 of cistern in 35 minutes. In how many minutes, it can fill 1/2 of the cistern?
Select.
A) 20 min
B) 25 min
C) 30 min
D) 35 min
E) 40 min

Rationale: "required time = 35 * 2 * 1 / 2 = 20 minutes answer is d"
Answer: D