In a group of students, 12 read maths, 15 read statistics, 11 read physics, 4 read maths only, 7 read statistics only, 3 read statistics and physics only and 1 read maths and statistics only. What is the number of the students who were there altogether (universal set)

23 students

Step-by-step explanation:

In a group of students, 12 read maths, 15 read statistics, 11 read physics, 4 read maths only, 7 read statistics only, 3 read statistics and physics only and 1 read maths and statistics only.

Those that read maths only = 4, Those that read statistic only = 7, Those that read statistics and physics only = 3, those that read maths and statistics only = 1.

Therefore those that read all three subjects = 15 - 7 - 3 - 1 = 4

Those that read maths and physics only = 12 - 4 - 4 - 1 = 3

Those that read physics only = 11 - 3 - 4 - 3 = 1

The number students = 4 + 7 + 3 + 1 + 4 + 3 + 1 = 23 students