We know the distance formula; d = rt where, d = distance; r = rate; t = time Solving for time (t) => t = d/r
Let x = speed of current t1 =Time going downstream = 120/(18+x) t2 =Time going upstream = 24/(18-x)
Since the boat travels 120 miles downstream in the same time it travels 8 miles upstream we can set t1 and t2 equal to each other and solve for x. 120/(18+x) = 24/(18-x) Cross mulitply and we have: 120(18-x) = 24(18+x) Simplify by dividing both sides by 24: 5(18-x) = (18+x) 90 - 5x = 18 + x => 90 = 18 + 6x => 72 = 6x => x =12 Therefore, Speed of current = 12 mph
Hope this helps, and if it does don't forget to "best" my answer! :)
Dec 3rd, 2014
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