PHYSICS

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A girl rows 10 km downstream in 2 h. Her return trip takes 4 h. How fast can she row in still water. in km/h?

  • PHYSICS -

    rowing speed = v

    speed upstream = (v-c)
    speed downstream = (v+c)

    (v+c) * 2 = 10
    (v-c) * 4 = 10 or (v-c) * 2 = 5

    2 v + 2 c = 10
    2 v - 2 c = 5
    ------------------add
    4 v = 15
    v = 15/4 = 3.75 km/hr

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