Kellen 's boat travels 15 mph. find the rate of the river current if she can travel 2 mi upstream in the same amount of time she can go 4 mi downstream. (let xequalsthe rate of the current.)

If the speed of the stream is x

Time is given by d/r, where r is the rate and d is the distance;

Rate for upstream = (15-x) mph and that of down stream is (15 + x) mph

The time taken will be the same;

Thus; 2 / (15-x) = 4 / (15+x)

cross multiplying;

30 + 2x = 60 - 4x

6x = 30

x = 5

Therefore the rate of the river is 5 mph