Question

Among 18 students in a room, 7 study mathematics, 10 study science, and 10 study computer programming. Also, 3 study mathematics and science, 4 study mathematics and computer programming, and 5 study science and computer programming. We know that 1 student studies all three subjects. How many of these students study none of the three subjects?

Answer 1

Answer:

2 students study none of the subjects.

Step-by-step explanation:

Consider the attached venn diagram. First, we place that 1 student studies the three subjects. Then, we notice that 3 students study math and science, then 2 students study math and science only, since we have 1 that studies the three subjects. In the same fashion, we have that 3 students study Math and computer programming only (since they are 4 in total). Note that since 7 students study math, and we already have 6 students in our count in the math subject this implies that 1 student studies only math (the total number of students inside the math circle must add to 7).

We also have that 4 students study science and computer programming only. Which implies that we must have 3 students that study science only (10 students that study science in total) and 2 students study computer programming (for a total of 10 students). The total number of students that study none is the total number of students (18) minus the amount of students that is inside the circles (16) which is 2.

Answer 2

Answer: 3 students study none of the three subjects

Step-by-step explanation:

The Venn diagram representing the situation is shown in the attached photo.

M represents the sub set of mathematics students.

S represents the sub set of science students.

CP represents the sub set of computer programming students.

From the diagram,

The number of students studying mathematics and science only is

3 - 1 = 2

The number of students studying mathematics and computer programming only is

4 - 1 = 3

The number of students studying science and computer programming only is

5 - 1 = 4

The number of students studying mathematics only is

7 - (2 + 1 + 3) = 1

The number of students studying mathematics only is

10 - (2 + 1 + 4) = 3

The number of students studying computer programming only is

10 - (3 + 1 + 4) = 2

Let x represent the number of students that study none of the three subjects. Since the total number of students is 18, it means that

2 + 3 + 4 + 1 + 3 + 2 + x = 18

15 + x = 18

x = 18 - 15 = 3