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