Question

теплоход сосна скорость которого 18 километров час прошел 50 километров по течению реки и 8 километров против течения за тратишь на весь путь в 3 часа какова скорость течения реки​

Answer 1

Ответ:

Пошаговое объяснение:

x - скорость течения реки, км/ч.

50/(18+x) +8/(18-x)=3

(50·18-50x+8·18+8x)/((18+x)(18-x))=3

18(50+8)-42x=3(324-x²)                          |3

348-14x=324-x²

x²-14x+348-324=0

x²-14x+24=0; D=196-96=100

x₁=(14-10)/2=4/2=2 км/ч

x₂=(14+10)/224/2=12 км/ч

Реальный ответ: 2.

Но задача, есть задача, например река Амазонка имеет среднюю скорость течения 15 км/ч.

Поэтому в этой задаче два ответа: 2 и 12.

Answer 2

Problem Analysis

We are given the following information: - The speed of a boat is 18 kilometers per hour. - The boat traveled 50 kilometers downstream (with the current) and 8 kilometers upstream (against the current). - The total time taken for the entire journey was 3 hours.

We need to find the speed of the river's current.

Solution

Let's assume the speed of the river's current is x kilometers per hour.

To find the speed of the river's current, we can set up the following equation based on the given information:

Downstream distance / (Boat speed + Current speed) + Upstream distance / (Boat speed - Current speed) = Total time

Substituting the given values: 50 / (18 + x) + 8 / (18 - x) = 3

Now, we can solve this equation to find the value of x.

Calculation

Let's solve the equation:

50 / (18 + x) + 8 / (18 - x) = 3

Multiplying both sides of the equation by (18 + x)(18 - x) to eliminate the denominators:

50(18 - x) + 8(18 + x) = 3(18 + x)(18 - x)

Expanding and simplifying:

900 - 50x + 144 + 8x = 3(324 - x^2)

1044 - 42x = 972 - 3x^2

Rearranging the equation:

3x^2 - 42x + 72 = 0

Now, we can solve this quadratic equation to find the value of x.

Using the quadratic formula: x = (-b ± √(b^2 - 4ac)) / (2a)

For our equation: a = 3, b = -42, c = 72

Substituting the values into the quadratic formula:

x = (-(-42) ± √((-42)^2 - 4 * 3 * 72)) / (2 * 3)

Simplifying:

x = (42 ± √(1764 - 864)) / 6

x = (42 ± √900) / 6

x = (42 ± 30) / 6

So, we have two possible solutions for x:

1. x = (42 + 30) / 6 = 72 / 6 = 12 2. x = (42 - 30) / 6 = 12 / 6 = 2

Therefore, the speed of the river's current can be either 12 kilometers per hour or 2 kilometers per hour.

Answer

The speed of the river's current can be either 12 kilometers per hour or 2 kilometers per hour.