Trains Boats and Streams Practice Test 1 with solutions

Question : 38 of 40

Marks: +1, -0

A boat sails down the river for 10 km and then up the river for 6 km. The speed of the current is 1 km/hour. What should be the minimum speed of the boat in a trip to take a minimum of 4 hours?

3.5 km/hour
5 km/hour
2.8 km/hour
4 km/hour
None of these

Validate

Solution:

Let the speed of the boat = x km/hour
According to the question,

6/{x-1}+{10}/{x+1}

= 4
6x + 6 + 10x - 10 = 4 (

x^2

- 1)
16x - 4 = 4 (

x^2

- 1)

x^2

- 4x = 0
x (x - 4) = 0
x = 4 km/hour

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