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Deepak Bora
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A motor boat whose speed is 18km/h in still water takes 1 hour more to go 24km upstream than to return downstream to the same spot. Find the speed of the stream.

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CBSE 10th Class Mathematics
Past year question paper
Year 2020
SET 1, Code Number  – 30/5/1
Question Number –  37 [b]
speed, distance and time problem
use the relation of speed, distance and time

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  1. Speed of boat = 18 km/h

    Let speed of the stream be =x km/h

    Speed of upstream = ( 18 – x ) km/hr

    Speed of downstream = ( 18 + x ) km/hr

    Distance = 24 km

    Time = Distance / Speed

    As per question,

    [24 / (18 – x)] – [24 / (18 + x)] = 1

    24 { [1 / (18 – x)] – [1 / (18 + x) ] } = 1

    [2x/(324 – x²)] = 1 / 24

    324 – x² = 48

    x² + 48x -324 = 0

    [x +54] [x – 6] = 0

    x = -54, x = 6

    x = 6 km / hr

    ∴ Speed of stream =6 km / hr

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