Question

Летом у феди на даче целые сутки было открыто окно в первый час влетел 1 комар во второй 2 в третий 3 и т.д.начиная со второго часа федя без сна и отдыха охотился за комарами.за второй час он убил 1 за третий 2 и т.д.сколько живых комаров осталось в комнате к концу суток .ответы а 0,б 24,в 20

Answer 1

Скаждым часом в комнате становилось на 1 комара больше соответсвенно 24 комара

Answer 2

Problem Analysis

Fedia's window was open for a whole day during the summer. In the first hour, 1 mosquito entered, in the second hour, 2 mosquitoes entered, and so on. From the second hour onwards, Fedia hunted mosquitoes without rest. In the second hour, he killed 1 mosquito, in the third hour, he killed 2 mosquitoes, and so on. The question is: how many live mosquitoes remained in the room by the end of the day?

Solution

To solve this problem, we need to calculate the number of mosquitoes that entered the room and subtract the number of mosquitoes that Fedia killed.

Let's break down the problem step by step:

1. Calculate the total number of mosquitoes that entered the room: - In the first hour, 1 mosquito entered. - In the second hour, 2 mosquitoes entered. - In the third hour, 3 mosquitoes entered. - And so on. - We can see that the number of mosquitoes that entered the room increases by 1 each hour. - So, the total number of mosquitoes that entered the room can be calculated using the formula for the sum of an arithmetic series: `n * (a + l) / 2`, where `n` is the number of terms, `a` is the first term, and `l` is the last term. - In this case, `n` is the number of hours (24), `a` is 1, and `l` is 24. - Plugging in the values, we get: `24 * (1 + 24) / 2 = 300` mosquitoes entered the room.

2. Calculate the total number of mosquitoes that Fedia killed: - In the second hour, he killed 1 mosquito. - In the third hour, he killed 2 mosquitoes. - In the fourth hour, he killed 3 mosquitoes. - And so on. - We can see that the number of mosquitoes that Fedia killed increases by 1 each hour, starting from the second hour. - So, the total number of mosquitoes that Fedia killed can also be calculated using the formula for the sum of an arithmetic series: `n * (a + l) / 2`, where `n` is the number of terms, `a` is the first term, and `l` is the last term. - In this case, `n` is the number of hours minus 1 (since Fedia started hunting from the second hour), `a` is 1, and `l` is 24. - Plugging in the values, we get: `23 * (1 + 23) / 2 = 276` mosquitoes were killed by Fedia.

3. Calculate the number of live mosquitoes remaining in the room: - To find the number of live mosquitoes remaining in the room, we subtract the number of mosquitoes killed by Fedia from the total number of mosquitoes that entered the room. - `300 - 276 = 24` live mosquitoes remained in the room by the end of the day.

So, the correct answer is 24 (option B).