Question 398415
One hose can fill a pool in 20 hours.  Another hose can fill the pool in 16 hours.  How long would it take the two hoses, working together to fill the pool?  
Here is how i set it up  t/20 + t/16 with a LCD of 2.  2 x (t/20 + t/16) = 2 x 1.  I reduced it down to  10t+8t=2, I combine my like terms this gives me 18t=2.  Now do i divide 18 into 2 or 2 into 18?  Am I on the right track to solving this problem?
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2 x (t/20 + t/16) = 2 x 1 this might work, but I don't know why you multiplied by 2
I do them like this:
The 1st hose fills 1/20 of the pool per hour
The 2nd does 1/16 per hour
Together, they do 1/20 + 1/16 = 9/80 per hour
9/80 pools per hour --> 80/9 hours per pool
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There's a shortcut, product/sum
16*20/(16+20) = 320/36 = 80/9 hours