In an examination a pupil’s average marks were 63 per paper. If he had obtained 20 more marks for his Geography paper and 2 more marks for his History paper, his average per paper would have been 65. How many papers were there in the examination?

A. 8
B. 9
C. 10
D. 11

Let the number of papers be x. Then,

63x + 20 + 2 = 65x
= 2x = 22
= x = 11