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