the average marks of a class of 30 students is 40 and that of another class of 50 students is 90 . 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 * 90 = 4500 sum of the marks for the class of 80 students = 1200 + 4500 = 5700 average marks of all the students = 5700 / 80 = 71.25 answer : a"
divide(add(multiply(30, 40), multiply(50, 90)), add(30, 50))