Question

В библиотеке на двух полках 120 книг. если в нижней переставить на верхнюю 15 книг ,то на нижней окажется в 3 раза больше книг, чем на первой. Сколько книг на нижней полке.

Answer 1

Х-15+(х-15)*3=120
3х-45+х-15=360
4х-60=360
4х=420
х=105 - на верхней полке

p.s.*-знак умножения 

Answer 2

Problem Analysis

We are given a library with two shelves containing a total of 120 books. If we move 15 books from the bottom shelf to the top shelf, the number of books on the bottom shelf will be three times the number of books on the top shelf. We need to determine how many books are on the bottom shelf.

Solution

Let's assume the number of books on the top shelf is x. According to the given information, the number of books on the bottom shelf will be 3x after moving 15 books from the bottom shelf to the top shelf.

We know that the total number of books in the library is 120. Therefore, we can set up the following equation to solve for x:

x + 3x + 15 = 120

Simplifying the equation:

4x + 15 = 120

Subtracting 15 from both sides:

4x = 105

Dividing both sides by 4:

x = 26.25

Since we can't have a fraction of a book, we need to round down to the nearest whole number. Therefore, there are 26 books on the top shelf.

To find the number of books on the bottom shelf, we can substitute the value of x into the equation:

3x = 3 * 26 = 78

Therefore, there are 78 books on the bottom shelf.

Answer

There are 78 books on the bottom shelf.