Question

В течении учебного года в школе трижды проводились соревнования по настольному теннису. В каждом соревновании принимало участие по 60 учащихся. При этом 70 учащихся только один раз участвовали в соревнованиях, 40 учащихся - ровно по два раза. Сколько учащихся все три раза принимали участие в соревнованиях? А. 10 Б. 12 В. 15 Г. 20

Answer 1

60*3 = 180 - всего учеников участвовало 180 - 40*2 - 70 = 30 30:3 = 10 Ответ: 10 учеников

Answer 2

Task: Calculate the number of students who participated in all three table tennis competitions.

To solve this problem, we need to find the number of students who participated in all three table tennis competitions.

According to the information provided, there were three competitions in total, and in each competition, 60 students participated. Additionally, 70 students participated in only one competition, and 40 students participated in exactly two competitions.

To find the number of students who participated in all three competitions, we can subtract the number of students who participated in only one or two competitions from the total number of participants in each competition.

Let's calculate it step by step:

1. Total number of participants in each competition: 60 students. 2. Number of students who participated in only one competition: 70 students. 3. Number of students who participated in exactly two competitions: 40 students.

To find the number of students who participated in all three competitions, we can subtract the number of students who participated in only one or two competitions from the total number of participants in each competition.

Total participants in three competitions: 60 * 3 = 180 students.

Number of students who participated in only one or two competitions: 70 + (40 * 2) = 150 students.

Number of students who participated in all three competitions: 180 - 150 = 30 students.

Therefore, the correct answer is 30 students.