Question

^Задание № 19. «Флажки» Девочкам из первого звена поручили сшить флажки для украшения спортзала к спортивному празднику. Ася, Лида и Лена одинаково быстро и хорошо умеют , выполнять эту работу. Если любые из этих двух девочек будут работать вместе, то выполнят эту работу за 2 часа 45 минут. А если они будут работать все трое вместе, сколько времени им понадобится?

Answer 1

1 час 50 мин будут работать 3 девочки

Answer 2

 

Для начала переведем время в минуты:

2ч45мин-165мин.

Решение:

1)165*2=330(мин)- выполнит первая  девочка

2)330/3=110 (мин)- выполнят три  девочки

 А теперь 110мин переведем в часы-1час 50 мин

Ответ: им понадобится 1час 50 минут

Answer 3

Problem Analysis

The problem states that Asya, Lida, and Lena can individually sew flags for decorating the sports hall. If any two of them work together, they can complete the task in 2 hours and 45 minutes. The question is how long it will take for all three of them to complete the task together.

Solution

To solve this problem, we can use the concept of work rates. Let's assume that the work rate of Asya is A, the work rate of Lida is L, and the work rate of Lena is E. We need to find the combined work rate of all three girls working together.

According to the problem, if any two of them work together, they can complete the task in 2 hours and 45 minutes. This means that the combined work rate of any two girls working together is twice the work rate of all three girls working together.

Let's calculate the combined work rate of Asya and Lida working together. Since they can complete the task in 2 hours and 45 minutes, their combined work rate is:

1 / (2 hours + 45 minutes)

Similarly, the combined work rate of Asya and Lena working together is:

1 / (2 hours + 45 minutes)

And the combined work rate of Lida and Lena working together is also:

1 / (2 hours + 45 minutes)

Now, let's add up the combined work rates of all three pairs:

Combined work rate of Asya and Lida + Combined work rate of Asya and Lena + Combined work rate of Lida and Lena = Combined work rate of all three girls

Let's solve this equation to find the combined work rate of all three girls.

Calculation

To calculate the combined work rate of all three girls, we need to convert the time of 2 hours and 45 minutes into hours. Since there are 60 minutes in an hour, 45 minutes is equal to 45/60 = 0.75 hours.

Now, let's substitute the values into the equation:

1 / (2 + 0.75) + 1 / (2 + 0.75) + 1 / (2 + 0.75) = Combined work rate of all three girls

Simplifying the equation:

1 / 2.75 + 1 / 2.75 + 1 / 2.75 = Combined work rate of all three girls

3 / 2.75 = Combined work rate of all three girls

Now, let's calculate the combined work rate of all three girls:

Combined work rate of all three girls = 3 / 2.75

To find the time required for all three girls to complete the task, we can use the formula:

Time = 1 / Combined work rate of all three girls

Let's calculate the time required:

Time = 1 / (3 / 2.75)

Time = 2.75 / 3

Time = 0.9167 hours

Answer

Therefore, it will take approximately 0.9167 hours for Asya, Lida, and Lena to complete the task together.

Note: The answer has been calculated based on the given information and assumptions.