Question

A motorboat whose speed is 18 km per hour in still water takes 1 hour more to go 24 km upstream then to return downstream to the same spot find the speed of stream

Answer 1

Answer:

Step-by-step explanation:

Let the speed of stream be x km / hr

For upstream = ( 18 - x ) km / hr

For downstream = ( 18 + x ) km / hr

A.T.Q.

24 / 18 - x - 24 / 18 + x = 1

48 x = 324 - x²

x² + 48 x - 324 = 0

( x + 54 ) ( x - 6 ) = 0

x = - 54 or x = 6

Since speed can't be negative .

Therefore , speed of the stream is 6 km / hr .

Answer 2

Answer:

Step-by-step explanation:

Solution :-

Let the speed of stream be x km/h.

Then, speed of boat upstream = (18 - x) km/h.

Speed of boat downstream = (18 + x) km/h.

According to the Question,

⇒ 24/(18 - x) - 24/18 - x = 1

⇒ 24(18 + x) - 24(15 - )/18² - x² = 1

⇒ 432 + 24x - 432 + 24x = 324 - x²

⇒ 48x = 324 - x²

⇒ x² + 48x - 324 = 0

⇒ x² + 54x - 6x - 324 = 0

⇒ x(x + 54) - 6(x + 54) = 0

⇒ (x + 54) (x - 6) = 0

⇒ x = - 54, 6 (As speed can't be negative)

⇒ x = 6 km/h

Hence, the speed of boat is 6 km/h.