Pratap Puri Rowed 22 miles

Question

Pratap Puri rowed 22 miles down a river in 2 hours, but the return trip took him 5 1/2 hours. Find the rate Pratap can row in still water and find the rate of the current. Let x=rate Pratap can row in still water and y=rate of the current

Answer 1

Let y = the speed of the water. Let x=his speed when rowing in still water.

distance = speed times time traveled d=st or s=d/t

He rowed downstream in 2 hours going 22 miles. That's d/t=22/2 = 11 mph = x+y

He rowed upstream in 5.5 hours doing the same 22 miles. That's d/t=22/5.5 mph = 2/.5 = 4 mph

4mph=x-y

you have 2 equations 2 unknowns, solve for one of the unknowns, x

x+y=11

x-y=4 add the 2 equations to eliminate y, getting

2x =15

x=15/2=7 1/2 mph

y=11-x=11-7.5=3.5 mph