A streamer going downstream in a river covers the distance between two towns in 20 hours. Coming back upstream it covers this distance in 25 hours. the speed of water is 4 km per hour . find the distance between two towns
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let speed of boat is x km/h and distance between two town is y km
net speed of boat in upstream=(x-4)km/h
net speed of boat in downstream
=(x+4) km/h
now,
according to question,
y/(x+4)=20
y=20 (x+4) ----------------(1)
y/(x-4)=25
y=25 (x-4) -------------------(2)
for equation (1) and (2)
20 (x+4)=25 (x-4)
20x+80=25x-100
180=5x
x=36 km/h
put x=36 in equation (1)
y=20 (36+4)=20 x 40
=800 km
net speed of boat in upstream=(x-4)km/h
net speed of boat in downstream
=(x+4) km/h
now,
according to question,
y/(x+4)=20
y=20 (x+4) ----------------(1)
y/(x-4)=25
y=25 (x-4) -------------------(2)
for equation (1) and (2)
20 (x+4)=25 (x-4)
20x+80=25x-100
180=5x
x=36 km/h
put x=36 in equation (1)
y=20 (36+4)=20 x 40
=800 km
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