I came across the following while doing some questions from my textbook.
For eg. lets say we need to calculate the total percentage of marks for the following subjects:
- Maths 64/100
- English 78/100
- Science 30/50
Total percentage being calculated as (64+78+30)/250 = 68.8 %
The other method I followed was to calculate individual percentages and then take their average
- Maths 64/100 = 64%
- English 78/100 = 78%
- Science 30/50 = 60%
Their average being (64+78+60)/3 = 67.33 %
I know by forming equations I can prove the second method is different from the first, but is there any logical statements that proves the second method is wrong and the first correct.