SOLUTION: Hi, I'm stuck on this one word problem, I want to know the steps in order to solve this problem so I am able to do it in the future. I'm currently working on Rational Expressions.

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Question 476875: Hi, I'm stuck on this one word problem, I want to know the steps in order to solve this problem so I am able to do it in the future. I'm currently working on Rational Expressions. Thank you!!!
In 3 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 7 minutes. If both belts are used, find how long it takes to move the cans to the storage area.
Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
You need to add their rates of working
to get their rate working together
For the bigger belt:
Rate1 = (300 pounds of aluminum) / (3 minutes)
For the smaller belt:
Rate2 = (300 pounds of aluminum) / (7 minutes)
I will call moving 300 pounds of aluminum 1 job
So, Rate1 = +1%2F3+
and Rate2 = +1%2F7+
Let t = time in minutes for both belts to do this job
Rate 1 + rate2 = Rate3
+1%2F3+%2B+1%2F7+=+1%2Ft+
Multiply both sides by 21t
+7t+%2B+3t+=+21+
+10t+=+21+
+t+=+2.1+ min
Note that +.1+ min = 6 sec
Working togethers, the belts can move the cans
in 2 min and 6 sec