4. 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
Answer:
Let the number pf papers be x.
Then, 63x + 20+2=65x
65x-63x=22
2x = 22
x = 11.
