SOLUTION: Noah can row 30 km downstream in 1.5 hr.Rowing upstream against the current he travels 12 km in 1.5 hr. Find the rate Noah rows and the rate of the current.

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Question 451550: Noah can row 30 km downstream in 1.5 hr.Rowing upstream against the current he travels 12 km in 1.5 hr. Find the rate Noah rows and the rate of the current.
Answer by pedjajov(51) (Show Source):
You can put this solution on YOUR website!
Formula for distance is r*t=d where

- r is a rate (speed) of movement of the object
- t is a time measured during the movement of the object
- d is a distance traveled during the movement of the object
We have to take in the rate of the river current - c.

So for the downstream we have:

(r+c)*t=d

Going upstream Noah travels against the current of the river, which rate we can mark as c) so the distance becomes

(r-c)*t=d, river slows down Noah

If we plug all the values we know we get

(r+c)*1.5=30
(r-c)*1.5=12

Dividing both equations by 1.5 we get

r+c=20
r-c=8

If we add these two equations we get

2r=28
r =14km/h, rate for Noah

Go back to find rate of the current:
r+c=20
c =20-r
c =20-14
c =6km/h

Rate for the river current is 6km/h.