Question

На первой полке в школьной библиотеке было в 2 раза больше книг, чем на второй, а на третьей на 15 книг меньше чем на второй. Сколько книг было на полках библиотеки, если всего книг было 105.

Answer 1

Ответ:

1 полка 60к  2 полка 30к 3 полка 15к

Пошаговое объяснение:

решение методом подбора

105:3=35 примерно 2 полка 30

35*2= 70 примерно 1 полка 60

105-(30+60)=15    3 полка

Answer 2

Problem Analysis

We are given information about the number of books on three shelves in a school library. The number of books on the first shelf is twice the number on the second shelf, and the number of books on the third shelf is 15 less than the number on the second shelf. We need to determine the total number of books on all three shelves, given that there are a total of 105 books in the library.

Solution

Let's assign variables to represent the number of books on each shelf: - Let x be the number of books on the second shelf. - The number of books on the first shelf is twice the number on the second shelf, so it is 2x. - The number of books on the third shelf is 15 less than the number on the second shelf, so it is x - 15.

According to the problem, the total number of books in the library is 105. We can write this as an equation:

x + 2x + (x - 15) = 105

Simplifying the equation:

4x - 15 = 105

Adding 15 to both sides:

4x = 120

Dividing both sides by 4:

x = 30

Now that we know the value of x, we can substitute it back into the expressions for the number of books on each shelf:

- Number of books on the first shelf: 2x = 2 * 30 = 60 - Number of books on the second shelf: x = 30 - Number of books on the third shelf: x - 15 = 30 - 15 = 15

Therefore, there are 60 books on the first shelf, 30 books on the second shelf, and 15 books on the third shelf.

Answer

There are a total of 60 books on the first shelf, 30 books on the second shelf, and 15 books on the third shelf in the school library.