Question

A race boat covers a certain distance of 66 km down stream in 110 min. It covers this distance upstream in 120 min. The speed of the boat in still water is 34.5 km/hr.find the speed of the stream.

Answer 1

Answer :

The speed of the stream is 1.5 km/hr.

Step-by-step explanation :

Given that :

A race boat covers a certain distance of 66 km down stream.

Time taken (down stream) =  110 minutes.

It covers this distance upstream in 120 minutes.

The speed of the boat in still water is 34.5 km/hr.

To Find :

The speed of the stream.

Solution :

$\bigstar \textbf{\underline{\underline{Consider as -}}}$

The speed of the stream as 'x' km/hr.

The racing boat is going downstream its speed as (34.5+x) km/hr

The racing boat is going upstream its speed as (34.5-x) km/hr.

We know that :

$\bigstar \boxed{\sf Speed = \dfrac{Distance}{Time}}}$

Plug the values :

$\tt \implies \dfrac{66}{(34.5+x)} = \dfrac{110}{60}\\ \\\implies (34.5+x) = 66\times 60\\ \\\implies (34.5+x) = 66\times\dfrac{60}{110} = 36\\ \\\implies x = 36-34.5 = 1.5 km/hr.$

It implies that the speed of the stream = 1.5km/hr.

$\rule{300}{1.5}$

★ Verification :

$\tt \implies \dfrac{66}{(34.5-x)}\\ \\\implies \dfrac{66}{(34.5-1.5)}\\ \\\implies \dfrac{66}{33} = 2hr\;and\; 120\;minutes. \\ \\\\\star \textbf{\underline{Our Answer is correct!}}$

Answer 2

♋♋YOUR ANSWERS♍♍

✍  1.5 km/h

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EXPLANATION —

Given -  

》Distance covered by boats in downstream = 66 km

》Time taken by boats to complete = 110 min

》Time taken to cover  upstream = 120 min

》speed of boat = 34.5 km/h  

To find—

》Speed of stream = ?  ________________________

Let speed of boat be x

Then speed of boat in downstream = 34.5 + x

Speed of boat in upstream = 34.5 - x  ____we have______

speed = Distance /time

=> 66/(34.5 + x)  =  110/60  

=> (34.5 + x)110 = 60 × 66

On solving  

=> x = 1.5 km/h  

Hence, the speed of stream is 1.5 km/h    ╒══════════════════════╕

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