We may think that the class is 25 students, in all,
of which 40%, or 10 students, are girls and the rest, 25-10 = 15 students, are boys.


Then the total score of girls is 10*82.3, while the total score of boys is 15*72.5.


Then the total score of the class is  10*82.3 + 15*72.5 = 1910.5.


Hence, the average score of the class is   = 76.42.


    Notice that this number 76.42 is the same as  0.4*82.3 + 0.6*72.5 = 76.42.


    So, we could get the answer using this simple formula (!)



ANSWER.  The average score of all the students in the class is 76.42.

Suppose there are 100 students.
40 girls and 60 boys.

Sum of scores of the 40 girls is 40*82.3=32920
Sum of scores of the 60 boys is 60*72.5=43500

Sum of scores of all 100 students = 3292+4350=7642

Average of all 100 students = 7642/100 = 76.42

Edwin