In an examination, the 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 numbers of girls and boys are in the ratio 4 : 5, what is the average marks of the whole class (approximately)?
Answer & explanation
Correct answer: option 4
The correct answer is Option (4) → 86.1
The class average is the total marks divided by the total number of students; the ratio 4 : 5 can be taken as 4 girls and 5 boys.
Total marks of 4 girls \(=4\times85=340\)
Total marks of 5 boys \(=5\times87=435\)
\(\displaystyle \text{Average}=\frac{340+435}{9}=\frac{775}{9}=86.11\ldots\)
The class average is about 86.1. It is nearer 87 than 85 because there are more boys.