What is the speed of the current?

Question

A motorboat can maintain a constant speed of 46 miles per hour relative to the water. The boat makes a trip upstream to a certain point in 53 minutes; the return trip takes 39 minutes. What is the speed of the current?

Answer 1

(46-c)(53/60)=(46+c)(39/60) where c=speed of the current

(2438/60)-(53c/60)=(1794/60)+(39c/60)

(2438/60)-(1794/60)=(53c/60)+(39c/60)

644/60=92c/60

since the denominators are equal, you can equate the numerators

92c=644

c=644/92

c=7 mph for the speed of the current