Question

Скорость катера по течению реки 21км против течения реки катер преодолевает 60 километров за 4 часа найдите скорость течения реки и собственную скорость катера

Answer 1

60:4=15 км/ч -скорость катера против течения
21-15=6 км/ч разница между скоростьями катера при движении по течению и против течения
6:2=3 км/ч скорость течения
15+3=18 км/ч собственная скорость катера

Answer 2

Problem Analysis

We are given the following information: - The speed of a boat against the current of a river is 21 km/h. - The boat covers a distance of 60 km in 4 hours.

We need to find: - The speed of the river current. - The speed of the boat in still water.

Solution

Let's assume the speed of the river current is x km/h and the speed of the boat in still water is y km/h.

To find the speed of the river current, we can use the formula: Speed of boat against the current = Speed of boat in still water - Speed of river current

From the given information, we know that the speed of the boat against the current is 21 km/h. Therefore, we can write the equation as: 21 = y - x ---(Equation 1)

We also know that the boat covers a distance of 60 km in 4 hours. This gives us the equation: 60 = (y + x) * 4 ---(Equation 2)

Now we have a system of two equations (Equation 1 and Equation 2) with two variables (x and y). We can solve this system of equations to find the values of x and y.

Solving the Equations

Let's solve the system of equations using the substitution method.

From Equation 1, we can express y in terms of x: y = 21 + x

Substituting this value of y in Equation 2, we get: 60 = (21 + x + x) * 4 60 = (21 + 2x) * 4 60 = 84 + 8x 8x = 60 - 84 8x = -24 x = -24/8 x = -3

Substituting the value of x in Equation 1, we can find y: 21 = y - (-3) 21 = y + 3 y = 21 - 3 y = 18

Answer

Therefore, the speed of the river current is 3 km/h and the speed of the boat in still water is 18 km/h.

Please note that the negative value for the speed of the river current indicates that the current is flowing in the opposite direction of the boat's motion.

Let me know if you need any further assistance!