Question

Старший брат, младший брат и сестра слепили снеговика за 12 минут.Старший брат может слепить его за 24 минуты, младший - за 40 минут. За сколько минут может слепить снеговика сестра?

Answer 1

В троем за 1 мин 1/12 часть работы
старший за мин - 1/24, младший - 1/40
Вместе -1/24+1/40=8/120=1/15
Сестра -1/12-1/15=1/60 (за 1 мин)
1час.

Answer 2

Problem Analysis

We are given that the older brother can build a snowman in 24 minutes, the younger brother can build it in 40 minutes, and they, along with their sister, built a snowman together in 12 minutes. We need to determine how long it would take the sister to build the snowman alone.

Solution

Let's assume that the sister can build the snowman in x minutes. We can set up the following equation based on the given information:

1/24 + 1/40 + 1/x = 1/12

To solve for x, we can multiply both sides of the equation by the least common multiple (LCM) of the denominators, which is 120x:

5x + 3x + 10 = 10x

Simplifying the equation:

8x + 10 = 10x

10 = 10x - 8x

10 = 2x

Dividing both sides by 2:

x = 5

Therefore, it would take the sister 5 minutes to build the snowman alone.

Answer

It would take the sister 5 minutes to build the snowman alone.