Question

a motorboat whose speed is 18 kilometre / hrs in still water takes 1 hour more to go 20 km upstream then to return downstream to the same pot. find the speed of the stream​

Answer 1

Answer:

Speed of boat = 18 km/h

Let speed of the stream be =x km/h

Speed of upstream = ( 18 – x ) km/hr

Speed of downstream = ( 18 + x ) km/hr

Distance = 24 km

Time = Distance / Speed

As per question,

[24 / (18 – x)] – [24 / (18 + x)] = 1

24 { [1 / (18 – x)] – [1 / (18 + x) ] } = 1

[2x/(324 – x²)] = 1 / 24

324 – x² = 48

x² + 48x -324 = 0

[x +54] [x – 6] = 0

x = -54, x = 6

x = 6 km / hr

✅∴ Speed of stream =6 km / hr✅

Step-by-step explanation:

❤plz follow❤

Answer 2

Let the speed of the stream be x km\hr.

The speed of the boat upstream = (18 - x) km/hr

The speed of the boat downstream = (18 + x) km/hr

Distance = 24 km

As given in the question,

Time for upstream = 1 + Time for downstream

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

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

x2 + 48x - 324 = 0

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

x ≠ - 54 as speed cannot be negative.

x = 6

The speed of the stream = 6 km/hr