Question

A​ boat's crew rowed 33kilometers​ downstream, with the​ current, in 3hours. The return trip​ upstream, against the​ current, covered the same​ distance, but took 11hours. Find the​ crew's rowing rate in still water and the rate of the current.

Answer 1

The crew rowing rate in still water = 7km/hr

The rate of the current = 4km/hr

Explanation:

The distance rowed downstream with the current = 33km

Time taken to row downstream = 3hrs

The distance rowed upstream against the current = 33km

Time taken to row upstream = 11hrs

Let the crew's rowing rate in still water = Xkm/hr

Let the rate of current = Ykm/hr

For the downstream movement, we will have (X+Y). This is because the boat rowed with the current

For the upstream movement, we will have (X-Y). This is because the boat rowed against the current

Downstream Speed = distance /time

= 33/3

= 11km

Upstream speed = distance /time

= 33/11

= 3km

Hence X+Y = 11 and X-Y= 3

Add both equations. We have

X+Y+X-Y = 11 + 3

2X = 14

X= 14/2

X= 7

put X= 7 in any of the equations

7-Y= 3

Y= 7-3

Y= 4

Hence the crew rowing rate in still water = 7km/hr and the rate of the current = 4km/hr