Question

A boat, which moves at 29 miles per hour in water without a current , goes 825 miles upstream and 825 miles back again in 58 hours. Find the speed of the current to the nearest the the place.

Answer 1

4 mph

Explanation:

Travel time is proportional to distance and inversely proportional to speed. If c represents the speed of the current in miles per hour, an equation for the total trip time is ...

825/(29 -c) +825/(29 +c) = 58 . . . . . . hours travel time

825(29 +c) +825(29 -c) = 58(29 -c)(29 +c)

58c² -928 = 0 . . . . . . . rearrange to standard form

58(c -4)(c +4) = 0 . . . . factor

Values of c that satisfy this equation are 4 and -4. For the purpose here, we'll choose the positive solution.

The speed of the current is 4 miles per hour.