Question

Пожааалууйстаааа срочно надоо помогитее Расстояние между двумя речными портами равно 60 км. Корабль проплывает это расстояние туда и обратно за 9 часов. Найдите скорость корабля в стоячей воде , если скорость течения реки равна 5км/ч.

Answer 1

60/(x+5)+60/(x-5)=9
(x-5)*(60/(x+5)+60/(x-5))=9*(x-5)
120x/(x+5)=9x-45
120x/(x+5)*(x+5)=(9x-45)*(x+5)
120x=9x^2-225
-9x^2+120x+225=0
D=120^2-4*(-9)*225=22500
x1=(√22500-120)/(2*(-9))=-5/3
x2=(-√22500-120)/(2*(-9))=15 км в час

Answer 2

#### Problem Analysis To find the speed of the ship in still water, we need to consider the effect of the river current on the ship's speed. The ship's speed in still water can be calculated by subtracting the speed of the river current from the total speed of the ship. #### Solution Let's assume the speed of the ship in still water is **x km/h**. The speed of the river current is given as **5 km/h**. When the ship is traveling downstream (from one port to another), it moves with the current, so its effective speed is the sum of its speed in still water and the speed of the current: **x + 5 km/h**. When the ship is traveling upstream (from the second port back to the first), it moves against the current, so its effective speed is the difference between its speed in still water and the speed of the current: **x - 5 km/h**. According to the problem, the ship covers a distance of **60 km** in both directions (to and from) in a total of **9 hours**. We can set up the following equation based on the given information: **60 km = (x + 5 km/h) * t + (x - 5 km/h) * t** Where **t** is the time taken for each leg of the journey (to and from). Simplifying the equation, we get: **60 km = 2x * t** Since the ship covers the same distance in both directions, the time taken for each leg of the journey is the same. Therefore, we can rewrite the equation as: **60 km = 2x * (9/2) hours** Simplifying further, we get: **60 km = 9x** Now, we can solve for **x**, the speed of the ship in still water: **x = 60 km / 9** Evaluating the expression, we find: **x ≈ 6.67 km/h** Therefore, the speed of the ship in still water is approximately **6.67 km/h**. #### Conclusion The speed of the ship in still water is approximately **6.67 km/h**.