Question

Мотоциклист должен попасть на работу к определенному сроку. известно, что если он поедет со скоростью 30 км/ч. то приедет на работу на 2 ч раньше, а если со скоростью 10 км/ч, то опоздает на 2 ч. с какой скоростью должен мотоциклист, что бы приехать вовремя

Answer 1

Так как про скорости 10 км/ч мотоциклист опаздывает на работу,
а при 30 км/ч приезжает раньше  ⇒ чтобы мотоциклист приехал вовремя, принимаем эту скорость за х: 10 км/ч<х<30 км/ч, а расстояние до работы
за единицу.  ⇒
1/(x-10)=1/(30-x)
30-x=x-10
2x=40
x=20
Ответ: 20 км/ч.
 

Answer 2

Хкм-расстояние
х/30+2=х/10-2
общий знаменатель30
х+60=3х-60
3х-х=60+60
2х=120
х=120:2
х=60км
60/30+2=4 часа должен ехать60Ж4=15км/ч
Ответ со скоростью 15 км/ч

Answer 3

Problem Analysis

A motorcyclist needs to arrive at work by a certain time. It is known that if the motorcyclist travels at a speed of 30 km/h, they will arrive 2 hours early. However, if they travel at a speed of 10 km/h, they will be 2 hours late. The question is: at what speed should the motorcyclist travel to arrive on time?

Solution

Let's assume the distance between the motorcyclist's starting point and their workplace is D kilometers. We need to find the speed at which the motorcyclist should travel to arrive on time.

If the motorcyclist travels at a speed of 30 km/h, they arrive 2 hours early. This means that the time it takes to travel the distance D at a speed of 30 km/h is D/30 hours less than the required time to arrive on time.

Similarly, if the motorcyclist travels at a speed of 10 km/h, they arrive 2 hours late. This means that the time it takes to travel the distance D at a speed of 10 km/h is D/10 hours more than the required time to arrive on time.

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

D / 30 = D / x - 2

Where x is the required speed in km/h.

Simplifying the equation, we get:

D / 30 = D / x - 2

D / 30 = (D - 2x) / x

Cross-multiplying, we get:

Dx = 30(D - 2x)

Expanding and rearranging the equation, we get:

Dx = 30D - 60x

60x - Dx = 30D

Factoring out x, we get:

x(60 - D) = 30D

Finally, solving for x, we get:

x = (30D) / (60 - D)

Now we can substitute the value of D to find the required speed.

Calculation

Since the problem does not provide the value of D, we cannot calculate the exact speed required. However, we can provide the formula to calculate the required speed based on the distance D.

The formula to calculate the required speed is:

x = (30D) / (60 - D)

Where x is the required speed in km/h and D is the distance between the motorcyclist's starting point and their workplace in kilometers.

Please provide the value of D to calculate the required speed.