A boat can travel 44 mph in still water. If it travels 147 miles with the current in the same length of time it travels 117 miles against the current, what is the speed of the current?
Let speed of current be C
Then average speed downstream (with current) = 44 + C
Also, average speed upstream (against current) = 44 - C
We then get the following TIME equation:
------ Reducing fractions by factoring out GCF, 3, in numerator
39(44 + C) = 49(44 - C) ------ Cross-multiplying
39(44) + 39C = 49(44) - 49C
39C + 49C = 49(44) - 39(44)
88C = 10(44)
C, or
It's as easy as A-B-C!