A worker can load one truck in 5 hours. A second worker can load the same truck in 8 hours. If both workers load one truck simultaneously while maintaining their constant rates, approximately how long, in hours, will it take them to fill one truck?  Select the correct option:
A) 2.5
B) 2.7
C) 2.9
D) 3.1
E) 3.3
The workers fill the truck at a rate of 1/5 + 1/8 = 13/40 of the truck per hour.   Then the time to fill one truck is 40/13 which is about 3.1 hours.   The answer is 3.1.
<result>D</result>
A worker can load one truck in 5 hours. A second worker can load the same truck in 8 hours. If both workers load one truck simultaneously while maintaining their constant rates, approximately how long, in hours, will it take them to fill one truck?