Maths

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A river flows at 3km/h. At what speed must a boat travel in order to make a 35km trip upstream in a time of 50 minutes?
How long will it take the boat to make the return trip downstream? (Assume the boat retains the speed travelled upstream)
Working out please

  • Maths -

    u = boat speed
    u-3 = upstream speed
    u+3 = downstream speed

    distance = speed * time

    35 = (u-3) * 5/6
    210 = 5u - 15
    225 = 5u
    45 = u

    downstream,

    35 = 48 * t
    t = 35/48
    t = 0.729 hr = 43min 45 sec

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