A motor boat,whose speed is 15 text{ km/hr} i | vedclass

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Question

(B) Let the speed of the stream be $x 	ext{ km/hr}$.Speed of the boat in still water = $15 	ext{ km/hr}$.Downstream speed = $(15 + x) 	ext{ km/hr}$

Vedclass · Accepted Answer

$5$

Vedclass · Answer

(B) Let the speed of the stream be $x 	ext{ km/hr}$.Speed of the boat in still water = $15 	ext{ km/hr}$.Downstream speed = $(15 + x) 	ext{ km/hr}$.Upstream speed = $(15 - x) 	ext{ km/hr}$.Total time taken = $4 	ext{ hours } 30 	ext{ minutes} = 4.5 	ext{ hours} = \frac{9}{2} 	ext{ hours}$.According to the problem,the total time for the round trip is:$\frac{30}{15+x} + \frac{30}{15-x} = 4.5$$\frac{30(15-x) + 30(15+x)}{(15+x)(15-x)} = 4.5$$\frac{450 - 30x + 450 + 30x}{225 - x^2} = 4.5$$\frac{900}{225 - x^2} = 4.5$$900 = 4.5(225 - x^2)$$200 = 225 - x^2$$x^2 = 225 - 200 = 25$$x = 5 	ext{ km/hr}$.

$A$ motor boat,whose speed is $15 \text{ km/hr}$ in still water,goes $30 \text{ km}$ downstream and comes back in a total of $4 \text{ hours } 30 \text{ minutes}$. The speed of the stream (in $\text{km/hr}$) is:

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