Question

В классе 28 учащихся, 15 человек посещают математический кружок, 12 биологический, 7 человек посещают оба эти кружка. Сколько учащихся не посещает ни один из этих кружков?А.6 Б.7 В.8 Г.9

Answer 1

15-7=8чел посещают только математич. кружок
12-7=5чел посещают только биологич. кружок
8+5+7=20чел посещают кружки
28-20=8чел не посещают кружки
ответ: в 8

Answer 2

Analysis

To find the number of students who do not attend either of the two clubs, we need to subtract the number of students who attend at least one club from the total number of students in the class.

Solution

Given: - Total number of students in the class: 28 - Number of students attending the math club: 15 - Number of students attending the biology club: 12 - Number of students attending both clubs: 7

To find the number of students who do not attend either club, we can use the principle of inclusion-exclusion. We start by adding the number of students attending each club and then subtract the number of students attending both clubs.

Number of students attending at least one club = Number of students attending the math club + Number of students attending the biology club - Number of students attending both clubs

Number of students attending at least one club = 15 + 12 - 7 = 20

Number of students not attending either club = Total number of students in the class - Number of students attending at least one club

Number of students not attending either club = 28 - 20 = 8

Therefore, the answer is В. 8.