Question

В 10 часов утра на стадионе было 28 человек ,из которых часть играли в футбол ,а часть -в волейбол.Затем семь из игравших в футбол ушли со стадиона ,а три человека,игравших в волейбол ,пошли играть в футбол .В результате играющих в футбол стало в два раза больше ,чем играющих в волейбол . Сколько человек играли в футбол в 10 часов утра ? Запиши решение и ответ .

Answer 1

Пусть в 10 часов утра в футбол играли х человек, а у человек играли в баскетбол.
Тогда х+у=28
Затем 7 человек,которые играли  в футбол, ушли со стадиона, тогда остались: х-7 человек.
3 человека ушли из волейбола, т.е.  у-3 и отправились играть в футбол: х-7+3=х-4 человек стали играть в футбол.

Составим и решим систему уравнений:
х+у=28
х-4=(у-3)*2

Выразим х из первого уравнения: х=28-у
Подставим его значение во второе уравнение:
28-у-4=(у-3)*2
24-у=2у-6
 -у-2у=-6-24
-3у=-30
у=10 (человек) - играли в волейбол
х=28-у=28-10=18 (человек) - играли в футбол.
Ответ: в 10 часов утра 18 человек играли в футбол.

Answer 2

Problem Analysis

We are given the following information: - At 10 o'clock in the morning, there were 28 people on the stadium. - Some of them were playing football, and the rest were playing volleyball. - Seven of those who were playing football left the stadium. - Three people who were playing volleyball started playing football. - As a result, the number of people playing football became twice the number of people playing volleyball.

We need to determine how many people were playing football at 10 o'clock in the morning.

Solution

Let's assume that the number of people playing football at 10 o'clock in the morning is x. Therefore, the number of people playing volleyball at that time would be 28 - x.

According to the given information, seven people who were playing football left the stadium, so the new number of people playing football is x - 7. Additionally, three people who were playing volleyball started playing football, so the new number of people playing football is x - 7 + 3.

According to the problem statement, the new number of people playing football is twice the number of people playing volleyball. Therefore, we can write the following equation:

x - 7 + 3 = 2(28 - x)

Simplifying the equation:

x - 4 = 56 - 2x

Bringing all the terms with x to one side:

x + 2x = 56 + 4

3x = 60

Solving for x:

x = 20

Therefore, there were 20 people playing football at 10 o'clock in the morning.

Answer

There were 20 people playing football at 10 o'clock in the morning.