Question

7. На полиці стояли книжки. Спочатку з полиці взяли 25 % книжок, а потім - 30 % книжок, що залиши- лися. Після цього на полиці залишилося 42 книжки. Скільки книжок було на полиці спочатку?​

Answer 1

Ответ:

80

Пошаговое объяснение:

42 книжки это 70% значит х/42=100/70

х=(100*42)/70=60

60 это количество книжек которое осталось после того как взяли 25% значит, что 60 книжек это 75% значит х/60=100/75

х=(100*60)/75=80 книжек

Answer 2

Problem Analysis

We are given that there were books on a shelf. Initially, 25% of the books were taken from the shelf, and then another 30% of the remaining books were taken. After these two actions, there were 42 books left on the shelf. We need to determine the initial number of books on the shelf.

Solution

Let's assume that the initial number of books on the shelf is represented by the variable "x".

According to the problem, 25% of the books were taken from the shelf, which means that 75% of the books remained. This can be represented as 0.75x.

Then, another 30% of the remaining books were taken, which means that 70% of the books remained. This can be represented as 0.70 * 0.75x = 0.525x.

We are given that 42 books remained on the shelf, so we can set up the equation:

0.525x = 42

To find the value of x, we can divide both sides of the equation by 0.525:

x = 42 / 0.525

Evaluating this expression, we find that x = 80.

Therefore, there were 80 books on the shelf initially.

Answer

There were 80 books on the shelf initially.