The speed of a boat in still water is 15 km/hr. It can go 30 km upstream and return downstream to the original point in 4 hours 30 minutes. Find the speed of the stream.
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Let the speed of stream = xkm/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
★It is given that the speed of a boat in still water is 15 km/h.
★Since speed can not be negative, therefore, x = 5.
Thus the speed of stream is 5 km/h.
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