Question

От ленты сначала отрезали 0.3 её длины, а потом 4/7 остатка. После чего осталось 12м. Какой длины (в метрах) была начальная длина ленты?

Answer 1

Пусть  начальная длина ленты  $x$  метров.

По условию сначала отрезали 0.3 её длины, т.е $0,3x$  метров

Осталось

$x-0,3x=0,7x$   метров

Потом  отрезали 4/7 остатка,т. е       $\frac{4}{7}\cdot 0,7x=0,4x$

Осталось

$0,7x-0,4x=0,3x$

После чего осталось 12м

Уравнение

$0,3x=12$

$x=12:0,3$

$x=40$

О т в е т. 40 метров

Answer 2

Problem Analysis

To solve this problem, we need to determine the initial length of a ribbon given the information that 0.3 of its length was cut off first, followed by cutting off 4/7 of the remaining length. After these two cuts, the ribbon's length is 12 meters.

Solution

Let's break down the problem step by step:

1. First, we need to find the length of the ribbon after the first cut, where 0.3 of its length was cut off. To do this, we can subtract 0.3 times the initial length of the ribbon from the initial length. Let's represent the initial length of the ribbon as 'x'. The length after the first cut can be calculated as: - Length after first cut = x - 0.3x = 0.7x

2. Next, we need to find the length of the ribbon after the second cut, where 4/7 of the remaining length was cut off. We can represent the length after the first cut as '0.7x'. The length after the second cut can be calculated as: - Length after second cut = 0.7x - (4/7)(0.7x) = 0.7x - 0.4x = 0.3x

3. We are given that the length after the second cut is 12 meters. So we can set up the equation: - 0.3x = 12

4. To find the initial length of the ribbon, we can solve the equation for 'x': - x = 12 / 0.3 = 40

Therefore, the initial length of the ribbon was 40 meters.

Conclusion

The initial length of the ribbon was 40 meters.