How do you solve this algebra problem?

youhelpme-ihelpyouyouhelpme-ihelpyou
in Science & Mathematics

You drove from your home to Dallas at an average speed of 60 miles per hour and returned home at an average speed of 45 miles per hour. If the total driving time was 21 hours, how far is it from your home to Dallas?

Comments

  • mominsdmominsd

    rate x time = distance

    let x = time driving from home to Dallas, then 21 - x = time driving from Dallas to home

    First leg: rate = 60, time = x, so distance = 60x (rate x time)

    Second leg: rate = 45, time = 21 - x, so distance = 45 (21 - x)

    The two distances are equal, so:

    60x = 45 (21 - x) distribute

    60x = 945 - 45x add 45x to each side

    105x = 945 divide by 105

    x = 9

    But x = time, so go back, and distance from home to Dallas was 60x,

    plug in x = 9 to get distance = 540 miles

  • jun-agrudajun-agruda

    Distance (x):

    60x = 45(21 - x)

    60x = 945 - 45x

    105x = 945

    x = 9

    Answer: 9 miles

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