Question

a boat can cover 10 km upstream and 55km downstream in 6hr. if the stream is 1.5 km/hr . find the speed of the boat in still water.

Answer 1

Step-by-step explanation:

6 नेपोलियन के उदय को कैसे समझा जा सकता है?

Answer 2

Answer:

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We know that,

$speed = \frac{distance}{time}$

Speed of stream= 1.5km/hr

Let speed of boat in still water is x km/hr

Speed of the boat upstream= (x-1.5)km/hr

speed of boat downstream= (x+1.5)km/hr

Total time to travel both upstream and downstream= 6 hours.

Let, time taken to travel upstream= t

time taken to travel downstream= (6-t)

Now,

distance travelled upstream= 10 km

(x-1.5)×t= 10...........(1)

xt-1.5t= 20............(2)

Distance travelled downstream= 5 km

(x+1.5)×(6-t)= 5

6x+9-xt-1.5t= 5

6x-xt-1.5t= -4..........(3)

Adding equation (2) and (3) ,we get

(calculation do on your own)

t= 2x-2

Putting t= 2x-2 in equation (1)

(calculation do on your own)

(x+1)(2x-7)= 0

Therefore,

x+1=0

x= -1

or,

2x-7=0

$x = \frac{7}{2}$

x= 3.5

Hence, the speed of boat in still water is 3.5km/hr.

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