A student‘s marks were wrongly entered as 65 instead of 45. Due to this, the average marks for the class got increased by 1/3. The number of students in the class is:

Question

Question

This question was previously asked in

SSC CGL 2022 Tier-I Official Paper (Held On : 08 Dec 2022 Shift 3)

Answer 1

Given:

Average with the marks were counted 45 = x

Average when the marks were counted 65 = x+

Concept used:

x = x =

Here n is the total number of students.

Let the sum of marks of rest of the students

Calculation:

x =

nx = +45 {equation 1}

x + =

nx + = +65

Putting the value of nx from equation 1

+ 45 + = + 65

= 20

n = 60

∴ The number of students is 60.

Alternate Method

A student‘s marks were wrongly entered as 65 instead of 45, so 20 marks extra were distributed among students.

Due to this, the average marks for the class got increased by 1/3, so the number of students in the class = 20 × 3 = 60