Question

Сняли -25% потом -70% осталось-27 кн.сколько было с начало?

Answer 1

27-30%                                   90-75%
х - 100%                                  х - 100%
х= 27*100/30=90                      х=90*100/75=120

Answer 2

Всех книг было 100%

Сняли: 100% - (25% + 70%) = 5% - осталось

27 книг - 5%. Чтобы узнать, сколько книг было всего, сначала находим чему равен 1%, а потом умножаем на 100:

27 : 5 * 100 = 540 книг было всего.

Answer 3

Calculating the Initial Value

To calculate the initial value, we can use the following steps:

1. Calculate the value after the first decrease of 25%. 2. Then, calculate the value after the second decrease of 70%. 3. Finally, solve for the initial value.

Step 1: Calculate the Value After the First Decrease of 25%

To calculate the value after the first decrease of 25%, we can use the following formula: \[ \text{Value after 25% decrease} = \text{Initial value} - (\text{Initial value} \times 0.25) \]

Let's denote the initial value as \( x \). Then, the value after the first decrease is \( x - 0.25x = 0.75x \).

Step 2: Calculate the Value After the Second Decrease of 70%

To calculate the value after the second decrease of 70%, we can use the following formula: \[ \text{Value after 70% decrease} = \text{Value after 25% decrease} - (\text{Value after 25% decrease} \times 0.70) \]

Substituting \( 0.75x \) for the value after the first decrease, we get: \[ \text{Value after 70% decrease} = 0.75x - (0.75x \times 0.70) = 0.75x - 0.525x = 0.225x \]

Step 3: Solve for the Initial Value

We are given that the value after the second decrease is 27. Therefore, we can set up the equation: \[ 0.225x = 27 \]

Solving for \( x \): \[ x = \frac{27}{0.225} = 120 \]

The initial value was 120.