Question

на первом этаже в лифт вошли 19 человек. на каждом следущем этаже, кроме последнего, в лифт входили по1 человеку, а выходили по 3. когда лифт поднялся на последний этаж, в нём был один человек. сколько этажей в здании?а)6 б)9 в)10 г)11

Answer 1

Ответ:в)

1 этаж:19 чел

2 этаж:19+1-2=17 чел

3 этаж:17+1-2=15 чел

4 этаж:13 чел

5 этаж:11 чел

6 этаж:9 чел

7 этаж:7 чел

8 этаж:5 чел

9 этаж:3 чел

10 этаж:1 чел

Answer 2

Calculation of the Number of Floors in the Building

To determine the number of floors in the building, we can analyze the given information about the people entering and exiting the elevator on each floor.

1. On the first floor, 19 people entered the elevator. 2. On each subsequent floor, except for the last floor, 1 person entered the elevator, and 3 people exited the elevator. 3. When the elevator reached the last floor, only 1 person was inside the elevator.

Let's calculate the number of floors based on this information.

1. On the first floor, 19 people entered the elevator. 2. On each subsequent floor, 1 person entered the elevator, and 3 people exited the elevator. 3. When the elevator reached the last floor, only 1 person was inside the elevator.

To calculate the number of floors, we need to find the difference between the number of people who entered the elevator and the number of people who exited the elevator on each floor.

Let's start with the first floor: - 19 people entered the elevator.

On the second floor: - 1 person entered the elevator, and 3 people exited the elevator. - The net change in the number of people inside the elevator is -2 (1 entered - 3 exited). - The total number of people inside the elevator is now 19 - 2 = 17.

On the third floor: - 1 person entered the elevator, and 3 people exited the elevator. - The net change in the number of people inside the elevator is -2 (1 entered - 3 exited). - The total number of people inside the elevator is now 17 - 2 = 15.

We can continue this process until we reach the last floor, where only 1 person is inside the elevator.

Based on this information, we can conclude that the number of floors in the building is 6 (option a).

Please let me know if there's anything else I can help you with!