Question

The average marks of Sameer decreased by 1, when he replaced the subject in which he has scored 40 marks by the other two subjects in which he has just scored 23 and 25 marks respectively. Later he has also included 57 marks of Computer Science, then the average marks increased by 2. How many subjects were there initially?

Answer 1

Answer:

15

Step-by-step explanation:

Let the number of subjects be 'n' and average marks be 'x'.

Then, total marks = nx

Again (n + 1)(x – 1) = (nx – 40) + (23 + 25)

⇒ x – n = 9          ….. (1)

Further (n + 2)(x + 1) = (nx – 40) + (23 + 25) + 57

⇒ nx + 2x + n + 2 = nx + 65

⇒ 2x + n = 63              .... (2)

Solving equations (1) and (2), we get

n = 15 and x = 24.