【Question 13】
A class has a total of 52 students, of which 30 can swim, 35 can ride a bicycle, and 42 can play table tennis. How many students in this class can do all three sports at the very least?
【Analysis and Solution】
Counting, Principle of Inclusion-Exclusion.
30 people can swim, $52-30=22$ people cannot swim;
35 people can ride a bicycle, $52-35=17$ people cannot ride a bicycle;
42 people can play table tennis, $52-42=10$ people cannot play table tennis;
To find the minimum number of people who can do all three, we need to find the maximum number of people who cannot do at least one;
The maximum number of people who cannot do at least one is $22+17+10=49$;
The minimum number of people who can do all three is $52-49=3$.