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Chapter 4: Q. 18 (page 106)

A boat takes 3.0 hours to travel 30kmdown a river, then 5.0 hours to return. How fast is the river flowing?

Short Answer

Expert verified

The speed of the river is 2km/h.

Step by step solution

01

Step 1. Given information

The boat takes3.0hto travel 30km down a river, and it takes5.0h to cover the same distance in return.

02

Step 2. Explanation

The speed of the boat is during the downstream is, v+u=Dt

Here, v is the speed of the boat, u is the speed of the stream, D is the total distance, and t is the time of row.

v+u=30km3.0hv=10.0km/h鈭�u

The speed of the boat during upstream is,

v鈭�u=Dt

(10.0km/h鈭�u)鈭�u=30km5.0h2u=10.0km/h鈭�6.0km/hu=4.0km/h2=2.0km/h

Therefore, the speed of the river is 2km/h.

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