Question

in a class of 20 students, the average mark of the first 19 students is 25 and the last 19 is 26. if the first boy get 16 marks find the marks of the last boy

Answer 1

here right answer is 35

Answer 2

Average of first 19 students=

x1+ x2+..............+x19/19=25

x1+ x2+..............+x19=25*19

=475.....eq . 1

Average of last 19 students=

x2+x3+.............+x20/19=26

x2+x3+.............+x20=26*19

=494....eq.2

from eq. (2-1).....

x2+x3+............+x20=494

-. x1+x2+.............+x19=475

That's equal to x20-x1=19

Given x1=16

x20=35