One pump drains one-half of a pond in 2.5 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 choice from the following choices:
A) 1 hour
B) 1.2 hour
C) 3 hours
D) 1.25 hours
E) 6 hours
The tricky part here, I believed is one half hour = 1/2. Then everything would be easy.   We have the 1st pump working rate/hour = 1/2 : 5/2 = 1/5   Working rate of 2 pumps: 1/2 : 1/2 = 1.   Working rate of 2nd pump: 1 -1/5 = 4/5--&gt; Time taken for the 2nd pump to finish: 1 : 4/5 = 5/4= 
<gadget id="calculator">5/4</gadget>
<output>5/4 = around 1.25</output>
1.25 hours.   1.25 hours
<result>D</result>
One pump drains one-half of a pond in 2.5 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?