Question

The average marks of 20 students in a test is 45. Now a student with 70 marks is replaced by an another student and the average marks becomes 46, then find the average marks of another student and the student replaced?
1. 80 
2. 70
3. 90
4. 75

Answer 1

Correct Answer - Option 1 : 80 

Given:

The average marks of 20 students in a test = 45

Student with 70 marks replaced by another student average marks = 46

Formula Used:

 Average = Sum of all the values/Total number of values

Calculation:               

Let the marks of another student in the test be m

Total marks of 20 students in the test = 20 ×  45

⇒ 900

Now, Student with 70 marks is replaced with another student with m marks

⇒ 900 – 70 + m = 46 × 20

⇒ m = 920 – 830

⇒ m = 90

Average marks of another student and student replaced = (90 + 70)/2

⇒ 160/2

⇒ 80

∴ The average marks of another student and the student replaced in the test is 80.