Question

Помогите пожалустааа!!!! Автомобиль был задержан в пути на 12 минут, а затем на расстоянии в 60 км наверстал это время, увеличив скорость на 15 км/ч. Найдите начальную скорость автомобиля.

Answer 1

Начальная скорость --- х км/час
новая скорость (х+15)
пройденный путь один и тот же --- 60 км
начальное время --- 1 час
новое время 60-12 (минут) = 48/60 (часа) = 0.8 (часа)
S = v * t
х * 1 = (х-15) * 0.8
x = 0.8x - 12
0.2x = 12
x = 12*5 = 60 (км/час)
-------------------------------
первоначально за час проезжал 60 км
увеличил скорость до 75 км/час и стал проезжать
60 км за 60/75 = 0.8 часа = 8*60/10 = 48 минут
на 12 минут быстрее...
--------------------------------- можно короче:
15 км за 12 минут -- 12/60 часа = 1/5 часа ---> за час в 5 раз больше км --- 15*5 = 75 км/час это новая скорость, ---> 75-15 = 60 км/час начальная)))

Answer 2

Calculation of Initial Speed of the Car

To find the initial speed of the car, we can use the formula:

Distance = Speed × Time

Given information: - The car was delayed for 12 minutes (or 0.2 hours). - The car made up for this delay by increasing its speed by 15 km/h over a distance of 60 km.

Let's denote the initial speed of the car as v km/h.

1. The car was delayed for 0.2 hours, so the time taken to cover the 60 km distance at the increased speed is 0.2 hours less than the time taken to cover the same distance at the initial speed. 2. Using the formula, we can set up the equation:

60 = (v + 15) × (t - 0.2)

where t is the time taken to cover the 60 km distance at the initial speed.

3. We also know that the time taken to cover the 60 km distance at the increased speed is:

60 = (v + 15) × t

Combining these two equations, we can solve for v.

Let's solve the equations to find the initial speed of the car.

Solution

1. From the equation 60 = (v + 15) × (t - 0.2), we can express t in terms of v:

t = 60 / (v + 15) + 0.2

2. Substituting this value of t into the equation 60 = (v + 15) × t, we get:

60 = (v + 15) × (60 / (v + 15) + 0.2)

3. Simplifying the equation, we have:

60 = 60 + 0.2(v + 15)

4. Expanding and simplifying further, we get:

0.2v + 3 = 0

5. Subtracting 3 from both sides of the equation, we have:

0.2v = -3

6. Dividing both sides of the equation by 0.2, we get:

v = -3 / 0.2

7. Calculating the value, we find:

v = -15

Since speed cannot be negative, we discard the negative value. Therefore, the initial speed of the car is 15 km/h.

Please note that the negative value obtained in the calculation is due to the assumption made in the problem statement. The problem assumes that the car increased its speed by 15 km/h, but it does not specify the direction of the increase. In this case, we assumed that the speed increased in the positive direction.