In an examination, the average of marks was found to be 50. For deducting marks for computational errors, the marks of 100 candidates had to be changed from 90 to 60 each and so the average of marks came down to 45. The total number of candidates, who appeared in the examination was:

600

Let the total no. of candidates is x

ATQ,

             50x = (100 × 30) + 45x

                5x = 100 × 30

                  x = 600