Question

the motorboat goes down the stream of 30 kilometre and again returns to the starting point in a total time of 4 hours 30 minutes if the speed of the stream in 5 kilometre per hour then find the speed of the motor boat in still water​

Answer 1

Answer:

Let the speed of the stream be x km/hr. Then,

Speed downstream = (15 + x) km/hr,

Speed upstream = (15 - x) km/hr.

30 + 30 = 4 1

(15 + x) (15 - x) 2

900 = 9

225 - x2 2

9x2 = 225

x2 = 25

x = 5 km/hr

Answer 2

The speed of motor boat in still water is 15 km/hr.

Step-by-step explanation:

Let the speed of motor boat in still water be 'x'.

Speed of stream = 5 km/hr

Total distance = 30 km + 30 km = 60 km

Total time = 4 hours 30 minutes = $4\dfrac{1}{2}=\dfrac{9}{2}$

So, it becomes,

$D=\dfrac{t(x^-y^2)}{2x}\\\\60=\dfrac{9(x^2-5^2)}{2\times 2\times x}\\\\30\times 4x=9(x^2-25)\\\\120x=9x^2-225\\\\9x^2-120x-225=0\\\\x=\dfrac{-5}{3},15$

Hence, the speed of motor boat in still water is 15 km/hr.

# learn more:

the motorboat goes down the stream of 30 kilometre and again returns to the starting point in a total time of 4 hours 30 minutes if the speed of the stream in 5 kilometre per hour then find the speed of the motor boat in still water​

https://brainly.in/question/15434489