Speed of a boat in still water is 15 km/h. it goes 30 km upstream and returns back at the same point in 4 hours 30 minutes. find the speed of the stream.
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Answered by
11
speed of stream = x km/h
speed upstream = 15-x km/h
speed downstream = 15+x km/h
30/(15-x) + 30/(15+x) =4.5 =9/2
(15+x +15-x)/(15²-x²) =9/2 (1/30)
30/(225-x²) = 9/60
1/(225-x²) = 9/60 (1/30) =1/200
225-x² = 200
x² = 25
x= +5 or x =-5 km/h
speed upstream = 15-x km/h
speed downstream = 15+x km/h
30/(15-x) + 30/(15+x) =4.5 =9/2
(15+x +15-x)/(15²-x²) =9/2 (1/30)
30/(225-x²) = 9/60
1/(225-x²) = 9/60 (1/30) =1/200
225-x² = 200
x² = 25
x= +5 or x =-5 km/h
Answered by
7
Hey there!
Let speed of stream = x km/h
∴ Downstream speed = (15+x) km/h
∴ Upstream speed = (15-x) km/h
∴ 30/(15+x) + 30/(15-x) = 4 1/2
→ 900/225-x² = 9/2
→ 9x² = 225
→ x² = 25
→ x = 5
∴ Speed of stream = 5 km/h
Hope it Helps You!
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