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? asked in Science & MathematicsMathematics · 2 years ago

Can someone please help with this math question?

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3 Answers

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  • 2 years ago
    Favorite Answer

    Suppose the original trip took t hours. The distance traveled at 50 km/h was 50t km. You're told that the return trip took 15 min. (0.25 h) longer traveling at 50+6 = 56 km/h, That's a return distance of 56(6 + 0.25) km; and that this distance is 26 km longer than the original. So:

    56(t + 0.25) = 50t + 23

    56t + 14 = 50t + 23

    6t = 23 - 14 = 9

    t = 9/6 = 1.5 h

    That's the original driving time. The return trip was 0.25 hr longer:

    t + 0.25 = 1.75 h

    That's an hour and 45 minutes, or 105 minutes if you prefer.

  • 2 years ago

    Distance:

    d1 is distance he drove to friend's house

    d2 is distance he drove back

    Speed:

    v1 = speed to friend's house

    v2 = speed from friend's house

    Time:

    t1 = d1/v1

    t2 = d2/v2

    Things we know:

    d1 = d2 - 23km

    v1 = 50km/h

    v2 = 56km/h

    t1 = t2 - 0.25h (15min = 0.25h)

    Use this equation

    v1 = d1/t1

    where

    d1 = d2 - 23km

    t1 = t2 - 0.25km = d2/v2 - 0.25h

    v1 = (d2 - 23km)/(d2/v2 - 0.25h)

    Multiply by d2/v2 - 0.25h

    v1/v2 *d2 - 0.25h*v1 = d2 - 23km

    Plug in known values for v1 and v2

    50/56 d2 - 12.5km = d2 - 23km

    Multiply by 56

    50d2 - 700km = 56d2 - 1288km

    588km = 6d2

    d2 = 98km

    d1 = d2 - 23km

    d1 = 98km - 23km

    d1 = 75km

    t1 = d1/v1

    t1 = 75km/50km/h

    t1 = 1.5h

  • 2 years ago

    Recall: s = d/t → where s is the speed, d is the distance, t is the time

    On the way to his friend's house, Latif drives at an average speed of 50 km/h.

    s₁ = d₁/t₁ → where: s₁ = 50 km/h

    50 = d₁/t₁

    50.t₁ = d₁

    When he returns home, Latif takes a longer route that has better roads.

    s₂ = d₂/t₂ → he drives an extra 23 km, so: d₂ = d₁ + 23

    s₂ = (d₁ + 23)/t₂ → his average speed is 6 km/h higher, so: s₂ = s₁ + 6 = 56

    56 = (d₁ + 23)/t₂ → the journey takes him an extra 15 min, i.e. 0.25 h, → t₂ = t₁ + 0.25

    56 = (d₁ + 23)/(t₁ + 0.25)

    56.(t₁ + 0.25) = d₁ + 23 → recall: d₁ = 50.t₁

    56.(t₁ + 0.25) = 50.t₁ + 23

    56.t₁ + 14 = 50.t₁ + 23

    56.t₁ - 50.t₁ = 23 - 14

    6.t₁ = 9

    t₁ = 9/6

    t₁ = 1.5 hours

    t₁ = 1 h + 0.5 h

    t₁ = 1 h + 30 min ← to go to his friend's house

    Recall:

    t₂ = t₁ + 15 min

    t₂ = 1 h + 30 min + 15min

    t₂ = 1 h + 45 min ← to return home

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