Question

Мальчик на электросамокате проехал три четверти расстояния от дома до школы за час. С какой скоростью он двигался, если увеличив скорость на 25 км/ч, он за следующий час добрался до школы и вернулся в домой?

Answer 1

Ответ:

15 км/ч

Объяснение:

Обозначим расстояние от школы до дома за х, а скорость электросамоката за v, выразим времена

$\frac{3x}{4v}=1$ час и $\frac{2x}{v+25}=1$ час

Приравниваем левый части выражений

$\frac{3x}{4v}=\frac{2x}{v+25}$

$\frac{3}{4v}=\frac{2}{v+25}$

И находим отсюда v

$3(v+25)=8v$

$3v+75=8v$

$-5v=-75$

$v=15$ км/ч.

Answer 2

Calculation of the Boy's Speed

To calculate the boy's speed, we need to determine the total distance he traveled and the time it took him to cover that distance.

Given information: - The boy traveled three-quarters of the distance from home to school in one hour. - When he increased his speed by 25 km/h, he reached the school and returned home in the next hour.

Let's assume the total distance from home to school is D kilometers.

In the first hour, the boy covered three-quarters of the distance, which is 3/4 * D kilometers.

In the second hour, the boy covered the remaining one-quarter of the distance, which is 1/4 * D kilometers.

Since the total time taken is two hours, we can set up the following equation:

Time = Distance / Speed

For the first hour: 1 hour = (3/4 * D) / Speed1

For the second hour: 1 hour = (1/4 * D) / Speed2

To find the boy's speed, we can solve these two equations simultaneously.

Let's solve for Speed1 and Speed2:

Speed1 = (3/4 * D) / 1 hour

Speed2 = (1/4 * D) / 1 hour

Now, let's calculate the boy's speed.

Speed1 = (3/4 * D) / 1 hour

Speed2 = (1/4 * D) / 1 hour

Speed2 = Speed1 + 25 km/h

Substituting the values:

(1/4 * D) / 1 hour = ((3/4 * D) / 1 hour) + 25 km/h

Simplifying the equation:

(1/4 * D) = (3/4 * D) + 25 km/h

Multiplying both sides by 4:

D = 3D + 100 km/h

Subtracting 3D from both sides:

-2D = 100 km/h

Dividing both sides by -2:

D = -50 km/h

Since distance cannot be negative, there seems to be an error in the given information or calculation. Please double-check the values provided.

Please provide the correct information, and I will be happy to help you with the calculation.