Question

Из пункта А в пункт В вышли Саша и Маша, известно что Маша пришла на 5 часов раньше Саши. Найдите скорость Саши, если скорость Маши на 3км в час больше. Расстояние между пунктами А и В =30 км.

Answer 1

30/x-30/(x+3)=5
(30/x-30/(x+3))*x=5*x
90/(x+3)*(x+3)=5x*(x+3)
90=5x^2+15x
-5x^2-15x+90=0
D=-15^2-4*(-5)*90=2025
x1=(√2025-(-15))/(2*(-5))=-6
x2=(-√2025-(-15))/(2*(-5))=3
Ответ: скорость Саши 3 км в час

Answer 2

Problem Analysis

We are given that Sasha and Masha left point A and arrived at point B. It is known that Masha arrived 5 hours earlier than Sasha. The distance between points A and B is 30 km. We need to find Sasha's speed, given that Masha's speed is 3 km/h faster.

Solution

Let's assume Sasha's speed is x km/h. Since Masha's speed is 3 km/h faster, her speed is x + 3 km/h.

We can use the formula distance = speed × time to find the time it took for each person to travel from point A to point B.

For Masha: - Distance = 30 km - Speed = x + 3 km/h - Time = 30 km / (x + 3 km/h) = 30 / (x + 3) hours

For Sasha: - Distance = 30 km - Speed = x km/h - Time = 30 km / (x km/h) = 30 / x hours

We know that Masha arrived 5 hours earlier than Sasha, so we can set up the following equation:

30 / (x + 3) = 30 / x + 5

To solve this equation, we can cross-multiply:

30x = 30(x + 3) + 5x

Simplifying the equation:

30x = 30x + 90 + 5x

30x - 30x = 90 + 5x

0 = 90 + 5x

5x = -90

x = -18

Since speed cannot be negative, we can conclude that there is no valid solution for Sasha's speed.