Question

Каждый из 20 учеников 9-ого класса записались хотя бы на один из трёх кружков: математики, физики и истории. Известно,на кружок физики записалось всего 60% всех учеников класса, один из учеников записался на все три кружка, 15% учеников записались только на кружки математики и истории, 10% - только на кружок истории. Сколько учеников записалось только на кружок математики?

Answer 1

60% от 20 учеников = 12 - записались на физику; остаток - 8; 1 ученик - на все три кружка; остаток 7; 10% (2 ученика) - на историю - остаток 5; 15% (3 ученика) - на историю и математику - остаток 2. Ответ: только на математику записалось 2 ученика.

Answer 2

Task: Calculate the number of students who only signed up for the math club.

Given: - Total number of students in the 9th grade: 20 - Three clubs: math, physics, and history - 60% of all students signed up for the physics club - 1 student signed up for all three clubs - 15% of students signed up only for math and history clubs - 10% of students signed up only for the history club

To find: Number of students who signed up only for the math club

Solution:

Let's calculate the number of students who signed up for each combination of clubs and then find the number of students who signed up only for the math club.

1. Total number of students: 20 2. Number of students who signed up for all three clubs: 1 3. Number of students who signed up for the physics club: 60% of 20 = 12 4. Number of students who signed up only for math and history clubs: 15% of 20 = 3 5. Number of students who signed up only for the history club: 10% of 20 = 2

Now, let's calculate the number of students who signed up only for the math club.

Calculation:

Total students who signed up for math club = Total students who signed up for math and history clubs - Students who signed up for all three clubs - Students who signed up only for history club Total students who signed up for math club = 3 - 1 - 2 Total students who signed up for math club = 0

Answer:

No students signed up only for the math club.