the average marks of a class of 30 students is 40 and that of another class of 50 students is 70 . find the average marks of all the students ?
"sum of the marks for the class of 30 students = 30 * 40 = 1200 sum of the marks for the class of 50 students = 50 * 70 = 3500 sum of the marks for the class of 80 students = 1200 + 3500 = 4700 average marks of all the students = 4700 / 80 = 58.75 answer : d"
divide(add(multiply(30, 40), multiply(50, 70)), add(30, 50))