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Boat covered 110 km in downstream with 10% less of its usual speed in 5 hr, if still water speed of boat is 400% more than speed of current…

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Boat covered 110 km in downstream with 10% less of its usual speed in 5 hr, if still water speed of boat is 400% more than speed of current. Find time required by boat to cover 120 km in upstream with its usual speed?

A4.5 hours
B5.5 hours
C6.5 hours
D8.5 hours

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Discussion 1

CCommunity07 Jul 2019

Let speed of the stream be x km/hr

Let the speed of the boat in still water be 5x km/hr

Downstream = 6x km/hr

Upstream = 4x km/hr

Speed while going downstream = (90/100) × 5x + x = 5.5x

5.5x = 110/5 ⇒ x = 4

Time required to cover 120km upstream = 120/(4 × 4) = 7.5 hours