Resultant speed while traveling down stream = (u + v) mi/hr
Resultant speed while traveling up stream = (u - v) mi/hr
Distance traveled down stream / up stream = d = 63 mi
Time taken for the journey down stream = t1 = 7 hr
Time taken for the journey up stream = t2 = 9 hr
Using the above data, we have :
d = (u + v)t1 (down stream journey)
=> 63 = 7(u + v)
=> u + v = 63/7 = 9 ----------- (1)
d = (u - v)t2 (up stream journey
=> 63 = (u - v)9
=> u - v = 63/9 = 7 ---------- (2)
Adding (1) and (2), we have : 2u = 16
=> u = 8 ----------- (3)
=> speed of rowing = 8 mi/hr
Subtracting (2) from (1), we have : 2v = 2
=> v = 1 ----------- (4)
=> speed of current = 1 mi/hr