Question

Хулиган Вася живёт в двадцатиэтажном доме. После того как Вася однажды покатался в лифте, в нём стали работать только две кнопки: ( 5) " при нажатии на эту кнопку лифт поднимается на 5 этажей вверх, если это возможно" и (7) " при нажатии на эту кнопку лифт опускается на 7 этажей вниз, если это возможно ". Можно ли, пользуясь таким лифтом, попасть: а) с первого этажа на второй; б) со второго этажа на первый; в) с третьего этажа на двадцатый? Помогите пожалуйста решить.

Answer 1

Ответ:

Во всех трёх случаях ответ - можно.

Пошаговое объяснение:

Разъяснения в приложении.

Answer 2

Problem Analysis

Vasya lives in a 20-story building and the elevator in his building only has two buttons: one that goes up 5 floors and one that goes down 7 floors. The question is whether it is possible to reach certain floors using this elevator. We need to determine if it is possible to go from the first floor to the second floor, from the second floor to the first floor, and from the third floor to the twentieth floor.

Solution

Let's analyze each case separately:

a) Going from the first floor to the second floor: To go from the first floor to the second floor, Vasya can press the button that goes up 5 floors. This will take him to the sixth floor. From there, he can take the stairs to the second floor. Therefore, it is possible to go from the first floor to the second floor using this elevator.

b) Going from the second floor to the first floor: To go from the second floor to the first floor, Vasya can press the button that goes down 7 floors. This will take him to the ninth floor. From there, he can take the stairs to the first floor. Therefore, it is possible to go from the second floor to the first floor using this elevator.

c) Going from the third floor to the twentieth floor: To go from the third floor to the twentieth floor, Vasya can press the button that goes up 5 floors. This will take him to the eighth floor. From there, he can press the button that goes up 5 floors again, which will take him to the thirteenth floor. Finally, he can press the button that goes up 5 floors one more time, which will take him to the eighteenth floor. From there, he can take the stairs to the twentieth floor. Therefore, it is possible to go from the third floor to the twentieth floor using this elevator.

In conclusion, it is possible to go from the first floor to the second floor, from the second floor to the first floor, and from the third floor to the twentieth floor using this elevator.

I hope this helps! Let me know if you have any further questions.