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? Pick.
A) 1 hour
B) 1.1 hour
C) 3 hours
D) 5 hours
E) 6 hours
First pump drains 1/2 of the tank in 4 hours   so 8 hours it will take to drain the full tank.   Let, 2nd 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 1.1 hour
<result>B</result>
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?