A large kennel has a gate for dogs to enter and a gate for dogs to exit. The kennel can be filled with dogs who use the entrance in 5 hours. The exit gate can be used to empty the kennel in 15 hours. If it is desired that the kennel should be filled, from empty, exactly 6 hours after the entrance gate is opened at 9:30am, then at what time should the exit gate be opened ?  Choose the correct option:	A) 10:00am	B) 10:45am	C) 12:00pm	D) 12:30pm	E) 1:30pm
In 6 hours the entrance gate can accept the amount of dogs equal to 6*1/5 = 6/5 of the kennel. So, 1/5 more than necessary, which should be compensated by the exit gate. To ride the kennel 1/5 of the dogs the exit gate needs 15/5= 
<gadget id="calculator">15/5</gadget>
<output>3</output>
3 hours.   Therefore, the exit gate should be opened at 9:30am + 6 hours - 3 hours= 12:30pm.   Answer: 12:30pm.
<result>D</result>
A large kennel has a gate for dogs to enter and a gate for dogs to exit. The kennel can be filled with dogs who use the entrance in 5 hours. The exit gate can be used to empty the kennel in 15 hours. If it is desired that the kennel should be filled, from empty, exactly 6 hours after the entrance gate is opened at 9:30am, then at what time should the exit gate be opened ?