Question 835124
A troop of scouts hike to the scout cabin at the rate of 2 miles per hour. They ride back to headquarters at 18 miles per hour. If the round trip takes 10 hours, how far is headquarters from the cabin? 
This is the equation I found. However, I don't understand where the nine came from or why their dividing the distance.
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Equation:
time = distance/rate
time + time = time
(d/2) + (d/18) = 10 hrs
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d/2 = (9/9)(d/2) = 9d/18
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(9d/18) + (d/18) = 10 
10d/18 = 10 
d=18 miles

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Cheers,
Stan H.
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