One pump drains one-half of a pond in 4 hours, and then a second pump starts draining the pond. The two pumps working together finish emptying the pond in one-half hour. How long would it take the second pump to drain the pond if it had to do the job alone? Choose the correct option.
A) 1 hour  B) 1.1 hour  C) 3 hours  D) 5 hours  E) 6 hours

Rationale: "first pump drains 1 / 2 of the tank in 4 hours so 8 hours it will take to drain the full tank . let , 2 nd pump drains the full tank in a hours so both together can drain ( 1 / 8 + 1 / a ) part in 1 hour son in 1 / 2 hour they drain 1 / 2 * ( 1 / 8 + 1 / a ) part of the tank given that in 1 / 2 hour they drain 1 / 2 of the tank hence we can say 1 / 2 * ( 1 / 8 + 1 / a ) = 1 / 2 solving u get a = 8 / 7 = 1.1 hence answer is b"
Answer: B