Question

The respective ratio between speed of the boat upstream and speed of the boat downstream is 4:5. What is the speed of the boat in still water if it covers a distance of 450 metres downstream in 1.5 minutes?

Answer 1

Answer=4.5 m/s

Step-by-step explanation

Since Given Ratio of Upstream to Downstream=4:5

Let Speed in Upstream=4x

let Speed in Downstream=5x

Given Distance Travelled in Downstream=450 m

Time in Downstream=1.5 m=90 seconds

We know Speed=Distance/time

5x=450/90

5x=5

X=5/5

X=1

Speed in Upstream=4x=4×1=4 m/s

Speed in Downstream=5x=5×1=5m/s

Now Speed in Still water is AVERAGe of the both speeds.

How? Let Speed in Still water is xkm/h and Given in Downstream is 2 more than Still water ,Then Speed in Downstream=x+2 km/h. When there is Increase of Certain speed from Still water in Downstream.Then there will be also decrease of same unit of speed in Downstream from the Still water speed.

Since here given

4 m/s and 5 m/s

It's AVERAGe or speed in Still water=4.5 m/s

Means There is increase of 0.5 m/s in Downstream as well as 0.5 m/s decrease in Upstream.

$\boxed{\mathbf{\huge{Speed=4.5\:m/s}}}$