In 10 minutes, a conveyor belt moves 300 pounds of recyclable aluminum from the delivery truck to a storage area. A smaller belt moves the same quantity of cans the same distance in 30 minutes. If both belts are used, find how long it takes to move the cans to the storage area.

Let us calculate the speed of each conveyor belt. The bigger one does 300 pounds in 10 minutes, hence its speed is 300 pounds / 10 minutes=30 pounds/min. The smaller one needs 30 minutes, hence its speed is 300 pounds / 30 minutes=10 pounds/min. We see that the total speed of both machines if they work together is 30+10=40 pounds/min. We have then that the two machines together can transfer 300 pounds in 300/40=7.5 minutes.