Question

a student have average marks 64 in four subjects. if we add the marks of 5th subject into it, the average becomes 68. find his marks in 5th subject

Answer 1

Avg(4 subject) = sum of the marks of four subs / 4

sum of the marks of four subject = avg(4 sub) * 4

= 64*4

= 256

Now, let the marks of fifth subject be x

so, sum of the marks of 5 subject = avg(5 sub) *5

sum of marks of 4 subject + fifth sub = 68*5

256 + x = 340

x= 340 - 256

x = 84

Hence, the marks of his fifth subject is 84.