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Lv 4
? asked in Science & MathematicsMathematics · 8 years ago

NEED MATH GENIUSES! ASAP!?

I need help with this word problem:

Flying in still air, an airplane travels 550 km/h. It can travel 1200 km with the wind in the same time that it travels 1000 km against the wind. Find the speed of the wind.

Thanks guys!

4 Answers

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  • Bob B
    Lv 7
    8 years ago
    Favorite Answer

    The wind speed adds or subtracts from the airplane's speed. Since distance is rate times time, time is distance divided by rate:

    Tu = 1000 / (550 - w) [upwind, wind speed subtracts]

    Td = 1200 / (550 + w) [downwind, wind speed adds]

    Since the times are the same, equate the two right sides:

    1000 / (550 - w) = 1200 / (550 + w)

    Cross-multiply:

    1000(550 + w) = 1200(550 - w)

    Divide both sides by 200 for convenience:

    5(550 + w) = 6(550 - w)

    Multiply out:

    2750 + 5w = 3300 - 6w

    Add 6w to both sides:

    2750 + 11w = 3300

    Subtract 2750 from both sides:

    11w = 550

    Divide both sides by 11:

    w = 550 / 11 = 50

    The wind is blowing at 50 km/h.

  • 8 years ago

    Speed against the wind in time t = 1000/t = 550 - wind speed, w

    Speed along the wind in time t = 1200/t = 550 + wind speed, w

    Dividing, we get 1000/1200 = (550 - w) / (550 + w)

    or 10/12 = (550 - w) / (550 + w)

    or 10*(550 + w) = 12*(550 - w)

    or 5500 + 10w = 6600 - 12w

    or 22w = 1100

    or w, wind speed = 50 km/h

  • 8 years ago

    Solve[{(550 + x) t == 1200, (550 - x) t == 1000}, {x, t}]

    50km/h

  • 8 years ago

    50km/h

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