SOLUTION: 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

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Question 1102605: 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
Answer by greenestamps(13200) About Me  (Show Source):
You can put this solution on YOUR website!


If an additional 22 marks raised the average per paper by 2, then the number of papers was 22/2=11.

You don't need to do any calculations with the actual marks to find that answer. But if you want to, it might look like this:

let x be the number of papers

Then since the average mark was 63, the total number of marks was 63x

Now you are changing the total number of marks to 63x+20+2 = 63x+22.

The new average is 65:

%2863x%2B22%29%2Fx+=+65
63%2B22%2Fx+=+65
22%2Fx+=+2
x+=+11