Question

A motor boat whose speed is
9km/hr in still water goes 15 km
downstream and comes back in a
total time of 3 hours and 45
minutes. Find the speed of the
stream.
O A. 3 km/hr
O B.2 km/hr
O c. 1 km/hr
O D. None of these​

Answer 1

ANSWER

Letspeedofstream=xk m / h r

then(

9+x

1 5

)+(

9−x

1 5

)=3+(

4

3

)hour

1 5 (

81−x

2

9−x+9+x

)=(

4

1 5

)

7 2=8 1-x

2

∴x

2

=8 1-7 2

∴x=3 k m / h r

Answer 2

Answer:

Step-by-step explanation:

Let speed of stream=xkm/hr

then$(\frac{15}{9+x})$+$(\frac{15}{9-x})$ =3+$\frac{3}{4}$ hour

15$(\frac{9-x+9+x}{81-x^{2} })$=$\frac{15}{4}$

$72=81-x^{2}$$x^{2}=81-72$

$x=3km/hr$