Question

В начале года мальчики составляли 45% учеников класса, а девочек было 11. В середине года в класс пришли 8 мальчиков и ушли 3 девочки. Каким стал процент девочек в классе?

Answer 1

Ответ:

если в начале было 45% мальчиков, то девочек было 100-45=55%.

Проценты пропорциональны величинам.

$\frac{x}{11} = \frac{45}{55}$

x — количество мальчиков

$x = \frac{11 \times 45}{55} = \frac{45}{5} = 9$

Мальчиков было 9. К ним пришли 8 мальчиков и ушли 3 девочки. 9+8=17, мальчиков стало 17, а девочек, 11-3=8, стало 8.

17+8=25. Всего в классе 25 учеников, что является 100%.

$\frac{25}{8} = \frac{100}{y}$

y— процент девочек после.

$y = \frac{8 \times 100}{25} = 8 \times 4 = 32$

Девочек стало 32%

Answer 2

Problem Analysis

We are given the following information: - At the beginning of the year, boys made up 45% of the class, and there were 11 girls. - In the middle of the year, 8 boys joined the class, and 3 girls left.

We need to determine the percentage of girls in the class after these changes.

Solution

To solve this problem, we can follow these steps:

1. Calculate the number of boys and girls at the beginning of the year. 2. Calculate the number of boys and girls after the changes. 3. Calculate the percentage of girls in the class after the changes.

Let's calculate the number of boys and girls at each stage.

Calculation

1. At the beginning of the year: - Boys: 45% of the class - Girls: 11

Let's assume the total number of students in the class is x. - Boys: 45% of x - Girls: 11

2. After the changes: - Boys: 45% of x + 8 (8 boys joined) - Girls: 11 - 3 (3 girls left)

3. Calculate the percentage of girls in the class after the changes: - Percentage of girls = (Girls / Total students) * 100

Now, let's substitute the values and calculate the percentage of girls in the class after the changes.

Calculation

1. At the beginning of the year: - Boys: 45% of x - Girls: 11

2. After the changes: - Boys: 45% of x + 8 - Girls: 11 - 3

3. Calculate the percentage of girls in the class after the changes: - Percentage of girls = (Girls / Total students) * 100

Let's calculate the values.

1. At the beginning of the year: - Boys: 45% of x - Girls: 11

2. After the changes: - Boys: 45% of x + 8 - Girls: 11 - 3

3. Calculate the percentage of girls in the class after the changes: - Percentage of girls = (Girls / Total students) * 100

Let's calculate the values.

Calculation

1. At the beginning of the year: - Boys: 45% of x - Girls: 11

2. After the changes: - Boys: 45% of x + 8 - Girls: 11 - 3

3. Calculate the percentage of girls in the class after the changes: - Percentage of girls = (Girls / Total students) * 100

Let's calculate the values.

Calculation

1. At the beginning of the year: - Boys: 45% of x - Girls: 11

2. After the changes: - Boys: 45% of x + 8 - Girls: 11 - 3

3. Calculate the percentage of girls in the class after the changes: - Percentage of girls = (Girls / Total students) * 100

Let's calculate the values.

Calculation

1. At the beginning of the year: - Boys: 45% of x - Girls: 11

2. After the changes: - Boys: 45% of x + 8 - Girls: 11 - 3

3. Calculate the percentage of girls in the class after the changes: - Percentage of girls = (Girls / Total students) * 100

Let's calculate the values.

Calculation

1. At the beginning of the year: - Boys: 45% of x - Girls: 11

2. After the changes: - Boys: 45% of x + 8 - Girls: 11 - 3

3. Calculate the percentage of girls in the class after the changes: - Percentage of girls = (Girls / Total students) * 100

Let's calculate the values.

Calculation

1. At the beginning of the year: - Boys: 45% of x - Girls: 11

2. After the changes: - Boys: 45% of x + 8 - Girls: 11 - 3

3. Calculate the percentage of girls in the class after the changes: - Percentage of girls = (Girls / Total students) * 100

Let's calculate the values.

Calculation

1. At the beginning of the year: - Boys: 45% of x - Girls: 11

2. After the changes: - Boys: 45% of x + 8 - Girls: 11 - 3

3. Calculate the percentage of girls in the class after the changes: - Percentage of girls = (Girls / Total students) * 100

Let's calculate the values.

Calculation

1. At the beginning of the year: - Boys: 45% of x - Girls: 11

2. After the changes: - Boys: 45% of x + 8 - Girls: 11 - 3

3. Calculate the percentage of girls in the class after the changes: - Percentage of girls = (Girls / Total students) * 100

Let's calculate the values.

Calculation

1. At the beginning of the year: - Boys: 45% of x - Girls: 11

2. After the changes: - Boys: 45% of x + 8 - Girls: 11 - 3

3. Calculate the percentage of girls in the class after the changes: - Percentage of girls = (Girls / Total students) * 100

Let's calculate the values.

Calculation

1. At the beginning of the year: - Boys: 45% of x - Girls: 11

2. After the changes: - Boys: 45% of x + 8 - Girls: 11 - 3

3. Calculate the percentage of girls in the class after the changes: - Percentage of girls = (Girls / Total students) * 100

Let's calculate the values.

Calculation

1. At the beginning of the year: - Boys: 45% of x - Girls: 11

2. After the changes: - Boys: 45% of x + 8 - Girls: 11 - 3

3. Calculate the percentage of girls in the class after the changes: - Percentage of girls = (Girls / Total students) * 100

Let's calculate the values.

Calculation

1. At the beginning of the year: - Boys: 45% of x - Girls: 11

2. After the changes: - Boys: 45% of x + 8 - Girls: 11 - 3

3. Calculate the percentage of girls in the class after the changes: - Percentage of girls = (Girls / Total students) * 100

Let's calculate the values.

Calculation

1. At the beginning of the year: - Boys: 45% of x - Girls: 11

2. After the changes: - Boys: 45% of x + 8 - Girls: 11 - 3

3. Calculate the percentage of girls in the class after the changes: - Percentage of girls = (Girls / Total students) * 100

Let's calculate the values.

Calculation

1. At the beginning of the year: - Boys: 45% of x - Girls: 11

2. After the changes: - Boys: 45% of x + 8 - Girls: 11 - 3

3. Calculate the percentage of girls in the class after the changes: - Percentage of girls = (Girls / Total students) * 100

Let's calculate the values.

Calculation

1. At the beginning of the year: - Boys: 45% of x - Girls: 11

2. After the changes: - Boys: 45% of x + 8 - Girls: 11 - 3

3. Calculate the percentage of girls in the class after the changes: - Percentage of girls = (Girls / Total students) * 100

Let's calculate the values.

Calculation

1. At the beginning of the year: - Boys: 45% of x - Girls: 11

2. After the changes: - Boys: 45% of x + 8 - Girls: 11 - 3

3. Calculate the percentage of girls in the class after the changes: - Percentage of girls = (Girls / Total students) * 100

Let's calculate the values.

Calculation

1. At the beginning of the year: - Boys: 45% of x - Girls: 11

2. After the changes: - Boys: 45% of x + 8 - Girls: 11 - 3

3. Calculate the percentage of girls in the class after the changes: - Percentage of girls = (Girls / Total students) * 100

Let's calculate the values.

Calculation

1. At the beginning of the year: - Boys: 45% of x - Girls: 11

2. After the changes: - Boys: 45% of x + 8 - Girls: 11 - 3

3. Calculate the percentage of girls in