Question

Девочка каждый день читала одинаковое число страниц. Первую книгу она прочитала за 12 дней. Вторую за 7 дней. Сколько страниц в каждой книге, если во второй книге на 90 страниц меньше?

Answer 1

12-7=5 дней
90 страниц за 5 дней, это 18 страниц в день(90/5=18)
18•12=216 страниц в первой
18•7=126 во второй

Answer 2

Problem Analysis

We are given that a girl reads the same number of pages every day. She finished reading the first book in 12 days and the second book in 7 days. We need to find the number of pages in each book, given that the second book is 90 pages shorter than the first book.

Solution

Let's assume that the number of pages the girl reads every day is x.

The total number of pages in the first book can be calculated by multiplying the number of days it took to finish the book (12) by the number of pages read per day (x). This gives us the equation: 12x.

Similarly, the total number of pages in the second book can be calculated by multiplying the number of days it took to finish the book (7) by the number of pages read per day (x). This gives us the equation: 7x.

We are also given that the second book is 90 pages shorter than the first book. This can be expressed as: 12x - 7x = 90.

Simplifying the equation, we get: 5x = 90.

To find the value of x, we divide both sides of the equation by 5: x = 18.

Now that we know the value of x, we can substitute it back into the equations to find the number of pages in each book.

The number of pages in the first book is: 12x = 12 * 18 = 216.

The number of pages in the second book is: 7x = 7 * 18 = 126.

Therefore, the first book has 216 pages and the second book has 126 pages.

Answer

The first book has 216 pages and the second book has 126 pages.