Question

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

Answer 1

Будем считать частями.
1-весь объем работы. объем работы:t=s
1/12- общая скорость лепки в минуту
1/40- скорость лепки младшего брата
1/24 -  скорость лепки старшего брата
х- скорость лепки младшей сестры
1/40+1/24+х=1/12
х=10/120-3/120-5/120
х=2/120=1/60 - скорость лепки сестры в минуту, 
т.е. нужен 1 час, чтоб слепить целого снеговика

Answer 2

Problem Analysis

We are given that the older brother can build a snowman in 24 minutes and the younger brother can build it in 40 minutes. We need to determine how long it would take for the sister to build the snowman.

Solution

Let's assume that the sister can build the snowman in x minutes.

From the given information, we know that the older brother can build the snowman in 24 minutes, which means he can complete 1/24th of the snowman in 1 minute. Similarly, the younger brother can complete 1/40th of the snowman in 1 minute.

If we add up the work done by all three siblings in 1 minute, it should equal the work required to complete the snowman. Since they can complete the snowman in 12 minutes, the total work required is 1 snowman.

So, the equation becomes:

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

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

5x + 3x + 120 = 120x

Simplifying the equation:

8x + 120 = 120x

Subtracting 8x from both sides:

120 = 112x

Dividing both sides by 112:

x = 120/112

Simplifying the fraction:

x = 1.0714

Therefore, it would take the sister approximately 1.0714 minutes to build the snowman.

Answer

The sister can build the snowman in approximately 1.0714 minutes.