Period 1 has 15 students in it and a test average of 86%. Period 2 has 21 students in it and an average of 88%. Period 3 has 12 students in it and an average of 95%. Use weighted means to find the overall average of the classes.

Answer 1

total marks of students in period 1 = 86*15 = 1290
total marks of students in period 2 = 88*21 = 1748
total marks of students in period 3 = 95*12 = 1140

add them up, then divide by the total number of students.

Answer 2

87.3