Question

a boat covers 50km in 2 hours downstream and covers the same distance in 5 hours upstream then find the distance covered in 3 hours in still water

Please ans in details.

Answer 1

Answer:

in down stream, speed if boat = speed of boat in still water + speed of water.

in up stream, speed of boat = speed of boat in still water - speed of water.

so b+w=50/2

and b-w=50/5

these simplify to b+w=25 and b-w=10,

adding we get 2b=35

b=17.5 km/h.

in 5 hrs, the distance covered= 17.5 × 5= 87.5 km

Answer 2

Let the speed of boat in still water be x km/h

let the speed of the stream be y km/h

While going downstream, speed of the boat = (x+y) km/h

while going upstream, speed of the boat = (x-y) km/h

speed = distance / time

while downstream, speed = (x+y)

x+y = 50 / 2

x+y= 25 km/h

while upstream, speed = (x-y)

x-y = 50 / 5

x-y = 10 km/h

Adding both results

x+y+x-y=25+10

2x = 35

x= 35/2

x= 17.5 km/h

Therefore, speed of the boat in still water = 17.5 km/h

Distance covered in 3 hours in still water = 17.5 * 3 = 52.5 km