The average marks of 28 students in mathematics were 50.Eight students left the school and the average increased by 5.

What is the average marks obtained by the students  who left the school?

A)45 B)42.5 C)37.5 D)50.5

ANS:37.5

Let's solve this step by step considering you are in school:

Given:

The average marks of 28 students in mathematics were 50.

Eight students left the school and the average increased by 5.

Step 1: Initial Average Calculation

Initially, the average marks of 28 students were 50.

Total marks of 28 students = 28 * 50 = 1400.

Step 2: Average After Students Leave

After 8 students leave, there are 20 students left.

The average increases by 5, so the new average is 50 + 5 = 55.

Step 3: New Total Marks Calculation

Total marks of 20 students with the new average = 20 * 55 = 1100.

Step 4: Total Marks of Students Who Left

Total marks of the 8 students who left = Total marks before - Total marks after they left

Total marks of the 8 students who left = 1400 - 1100 = 300.

Step 5: Average Marks of Students Who Left

Average marks = Total marks of students who left / Number of students who left

Average marks = 300 / 8 = 37.5.

Therefore, the average marks obtained by the students who left the school is 37.5 (Option C).