Question

The average marks obtained by three students is 15. If two students obtained 12 and 18 marks respectively, find the marks obtained by the third student.​

Answer 1

We can clearly say that "mean" has been used.

• Mean is the average of a group of numbers.

In this case, we are given three numbers, 12, x, and 18.

• => 12 + 18 + x/3 = 15
• => 30 + x = 3 x 15
• => 30 + x = 45
• => x = 45 - 30
• => x = 15

The marks obtained by the third student is 15 marks.

Answer 2

15 marks

Explanation:

If the average mark obtained by 3 students is 15, then the total marks are

⇒ 3 x 15 = 45

Let x be the marks obtained by the third student.

If two students obtained 12 and 18 marks, then

⇒ 12 + 18 + x = 45

⇒ 30 + x = 45

⇒ x = 45 - 30

⇒ x = 15