the average marks of a class of 28 students is 40 and that of another class of 50 students is 60 . find the average marks of all the students ?
"sum of the marks for the class of 28 students = 28 * 40 = 1120 sum of the marks for the class of 50 students = 50 * 60 = 3000 sum of the marks for the class of 78 students = 1120 + 3000 = 4120 average marks of all the students = 4120 / 78 = 52.8 answer : c"
divide(add(multiply(28, 40), multiply(50, 60)), add(28, 50))