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**.