Question

Помогите пожалуйста! Пешеход должен был пройти 9 км с некоторой скоростью ,но увеличив эту скорость на 2 км/ч ,он прошел 9 км на 45 мин быстрее,какова истинная скорость пешехода.

Answer 1

Если я не ошибаюсь то можно придставить что 9км н прошёл за 45 минут и тогда 45/9=5 км\ч минус 2км\ч =3км\ч теперь растояние 9км / на скорость 3км\ч =3 часа

  

Answer 2

Calculation of True Walking Speed

To calculate the true walking speed of the pedestrian, we can use the given information that the pedestrian was supposed to walk 9 km at a certain speed, but by increasing the speed by 2 km/h, they were able to cover the same distance 45 minutes faster.

Let's denote the original speed of the pedestrian as x km/h.

According to the given information, the pedestrian was supposed to walk 9 km at speed x km/h. This would take them a certain amount of time.

When the pedestrian increased their speed by 2 km/h, they were able to cover the same distance of 9 km in 45 minutes less time.

To find the true walking speed, we can set up the following equation:

9 / x = 9 / (x + 2) + 45 / 60

Simplifying the equation, we get:

9 / x = 9 / (x + 2) + 3 / 4

To solve this equation, we can multiply through by the least common denominator, which is 4x(x + 2):

36(x + 2) = 36x + 9x(x + 2) + 3x(x + 2)

Expanding and simplifying the equation further:

36x + 72 = 36x + 9x^2 + 18x + 3x^2 + 6x

Combining like terms:

9x^2 + 27x - 72 = 0

Now we can solve this quadratic equation for x using the quadratic formula:

x = (-b ± √(b^2 - 4ac)) / (2a)

For our equation, a = 9, b = 27, and c = -72.

Plugging in these values, we get:

x = (-27 ± √(27^2 - 4 * 9 * -72)) / (2 * 9)

Simplifying further:

x = (-27 ± √(729 + 2592)) / 18

x = (-27 ± √(3321)) / 18

x = (-27 ± 57) / 18

This gives us two possible values for x:

x = (-27 + 57) / 18 = 30 / 18 = 5/3 ≈ 1.67 km/h

x = (-27 - 57) / 18 = -84 / 18 = -14/3 ≈ -4.67 km/h

Since the speed of the pedestrian cannot be negative, we can conclude that the true walking speed of the pedestrian is approximately 1.67 km/h.

Please note that the negative solution is extraneous and does not represent a valid speed in this context.