Question

an average score of a student in two papers is 50 and in three other papers is 75. what is the average of marks of the student in all five papers?

Answer 1

average marks scored in two papers = 50
So, the total marks scored in these two papers = 50 × 2 = 100 marks
average marks scored in other three papers = 75
So, the total marks scored in these three papers = 75 × 3 = 225 marks
Total marks scored in all the five papers = 100 + 225
= 325 marks
then, the average marks scored in all the five papers = 325/5
= 65 marks

Answer 2

let the scores in five papers be x1,x2,x3,x4 and x5
now..
average of 2 papers = 50
(x1+x2)/2=50
x1+x2=100 -----(1)
now
average of 3 papers = 75
(x3+x4+x5)/3=75
x3+x4+x5=225 -----(2)
now
average marks in all 5 papers
= (x1+x2+x3+x4+x5)/5
=(100+225)/5. [from (1) & (2)]
=325/5
=65
therefore the average score of a student in all five papers is 65

hope this helps:p