SOLUTION: One crew can put up holiday decorations in the mall in 9 hours. A second crew can put up the decorations in 7 hours. How long will it take if both crews work together to decorate t

Question 16110: One crew can put up holiday decorations in the mall in 9 hours. A second crew can put up the decorations in 7 hours. How long will it take if both crews work together to decorate the mall? Please enter your answer as a number without the units.
Answer by fractalier(6550) (Show Source): You can put this solution on YOUR website!
We use the equation
t/A + t/B = 1
now plug in to solve for t...
t/7 + t/9 = 1
multiply by the LCD, 63, and get
9t + 7t = 63
16t = 63
t = 63/16 hours or
t = 3 15/16 hours if you need it mixed...
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