It takes 6 beavers 10 hours to build a certain dam, working at a uniform rate. If seven beavers start to build the same dam at noon, and one beaver per hour is added beginning at 6:00 PM, at what time will the dam be complete?
Pick.
A) 7:24 PM B) 7:48 PM C) 8:06 PM D) 8:32 PM E) 9:12 PM
The rate of 1 beaver is 1/60.   The amount of work done by 7 beavers in 6 hours is 7/60 *6 = 42/60   In the next hour, 8 beavers do 8/60 for a total of 50/60.   In the next hour, 9 beavers do 9/60 for a total of 59/60.   In the next 6 minutes, 10 beavers do 10/60 * 6/60 = 1/60 for a total of 60/60.   The dam will be completed at 8:06 pm.   The answer is 8:06 PM.
<result>C</result>
It takes 6 beavers 10 hours to build a certain dam, working at a uniform rate. If seven beavers start to build the same dam at noon, and one beaver per hour is added beginning at 6:00 PM, at what time will the dam be complete?