In an examination average marks obtained by the girls of a class is 85 and the average marks obtained by the boys of the same class is 87. If the girls and boys are in the ratio 4 : 5, average marks of the whole class (approx.) is closest to :

A. 86.5

B. 85.9

C. 86.4

D. 86.1

Answer: Option D

Solution(By Examveda Team)

Average of whole class
$$\eqalign{ & = \frac{{85 \times 4 + 87 \times 5}}{{5 + 4}} \cr & = \frac{{340 + 435}}{9} \cr & = \frac{{775}}{9} \cr & = 86.1 \cr} $$