Two pipes A and B can fill a tank in 36 hours and 46 hours respectively. If both the pipes are opened simultaneously, how much time will be taken to fill the tank?
Choose the correct choice from the following answers: A) 20.195 hrs B) 21.195 hrs C) 22.195 hrs D) 23.195 hrs E) 20.495 hrs

Rationale: "a fill in one hour = 1 / 36 b fill in one hour = 1 / 46 both fill in one hour = 1 / 36 + 1 / 46 = 82 / 1656 time taken by both pipes = 1656 / 82 = 20.195 hrs answer : a"
Answer: A