Question

Вчера Саша прочитал 1/7 книги, а сегодня ещё 2/21 книги. Если он прочтёт ещё 55 страниц, то до конца ему останется прочесть половину книги. Сколько страниц в этой книге?

Answer 1

х - половина книги

2х - вся книга

х-2х*1/7-2х*2/21=55

х-2/7х-4/21х=55

(21х-6х-4х)/21=55

11х=55*21

11х=1155

х=1155:11

х=105 стр - половина

105*2=210 стр - вся книга

Answer 2

Ответ:

В книге 210 страниц.

Пошаговое объяснение:

Составим урпвнение

Х/2=х/7+2х/21+55 ;

Х=210 ;

Проверяем

Половина книги 105 стр.

210/7+210*2/21+55=105.

Задача решена

Answer 3

Problem Analysis

Sasha read 1/7 of a book yesterday and an additional 2/21 of the book today. If he reads another 55 pages, he will have read half of the book. We need to determine the total number of pages in the book.

Solution

Let's assume the total number of pages in the book is x.

According to the given information: - Yesterday, Sasha read 1/7 of the book, which is equal to 1/7 * x pages. - Today, Sasha read an additional 2/21 of the book, which is equal to 2/21 * x pages. - If Sasha reads another 55 pages, he will have read half of the book, which is equal to 1/2 * x pages.

To find the total number of pages in the book, we can set up the following equation:

1/7 * x + 2/21 * x + 55 = 1/2 * x

Let's solve this equation to find the value of x.

Step 1: Combine like terms on the left side of the equation: 3/21 * x + 2/21 * x + 55 = 1/2 * x

Step 2: Combine the fractions on the left side of the equation: 5/21 * x + 55 = 1/2 * x

Step 3: Multiply both sides of the equation by 2 to eliminate the fraction: 10/21 * x + 110 = x

Step 4: Move all terms involving x to one side of the equation: 10/21 * x - x = -110

Step 5: Simplify the left side of the equation: -11/21 * x = -110

Step 6: Multiply both sides of the equation by -21/11 to solve for x: x = (-110) * (-21/11) x = 210

Therefore, the total number of pages in the book is 210.

Answer

The book has a total of 210 pages.