Question

На полке стояли книги. Сначала с полки сняли 25% всех книг,а потом 70% оставшихся книг. После этого на полке осталось 27 книг . Сколько книг было на полке первоначально .

Answer 1

1 - 70 =30%=0,3 это оставшиеся 27 книг
27:0,3=90книг осталось после того как сняли книги в первый раз
1 - 25=75%=0,75 это оставшиеся 90 книг
90:0,75=120книг стояло на полке первоначально

Answer 2

Problem Analysis

We are given that there were books on a shelf. First, 25% of all the books were removed from the shelf, and then 70% of the remaining books were removed. After these two removals, there were 27 books left on the shelf. We need to determine the initial number of books on the shelf.

Solution

Let's assume the initial number of books on the shelf is x.

After removing 25% of the books, we have x - 0.25x = 0.75x books remaining.

Then, after removing 70% of the remaining books, we have 0.75x - 0.7(0.75x) = 0.225x books remaining.

We are given that there are 27 books remaining, so we can set up the equation:

0.225x = 27

To find the value of x, we can solve this equation:

x = 27 / 0.225

Let's calculate the value of x:

x = 27 / 0.225 = 120

Therefore, the initial number of books on the shelf was 120.

Answer

The initial number of books on the shelf was 120.