There are A girls in a class, and their average height is M inches. In the same class, there are Y boys with an average height of N inches. What is the average height of all the students in the class?
Choose the most appropriate option
A) (X + Y)/(M + N) B) (M + N)/(X + Y) C) (XM + YN)/(M + N) D) (AM + YN)/(A + Y) E) MN/XY
Total height = AM+YN   No of students = X+Y   Avg = (AM+YN)/(A+Y)   Answer is (AM + YN)/(A + Y)
<result>D</result>
There are A girls in a class, and their average height is M inches. In the same class, there are Y boys with an average height of N inches. What is the average height of all the students in the class?