Hi in the session we are going to learn about weighted averages for this let us take an example which you must be familiar with let say there are 3 subjects maths science and languages let’s say you scored 60% in maths 70% in Science and 80% in languages the question is what’s the average percentage marks you scored in these 3 subjects will it be 60 + 70 + 80 divided by 3 the simple average which is nothing but 70% what do you think well that will be true only if all the subjects are out of hundred marks or they are out of equal marks am I right or wrong what if I change the weightages of each subject for example let’s say maths is out of 200 marks science out of 300 and languages out of 500 will the answer still be 70% not really because now I will calculate the individual marks in each subjects for example in maths you would have scored 60% of 200 which is 120 in science you would have scored 70% of 300 which is 210 and in languages you whould have scored 80% of 500 which is 400 the sum total of the marks is 120 + 210 + 400 divide by the over all marks which is 200 + 300 + 500 this is how you will calculate the percentage right and it turns out to be 73% now the question is why isn’t it 70% reason is pretty simple in the earlier case We had assumed that all subjects were equally important because all subject had equal marks with this stand you realise that languages the scores that you scored in this subject must be given more importance because it is out of 500 marks as compared to maths which is only out of 200 marks and hence what we have here is a concept of weighted average so we’ll have to assign some ways to each of these scores for example since their marks are in ratio 2:3:5 will assign the weightages of 2, 3 and 5 respectively to the respective percentages which is 60, 70, 80 which means the average percentage marks will be calculated as 2*60 + 3*70 + 5*80 upon the sum of the weights which is 2 + 3 + 5 and that turns out to be 73% now this concept is what we call the weighted average where in different values are assign different weights depending on their importance let us understand this even better using this example if 3kgs of tea powder costing 10 rupees per kg is mixed with 2kg of tea powder costing 25 rupees per kg what will be the average price of the resulting mixture right now we have two varieties of tea powder