The average weight of 25 boys in a class is 48 kg and the average weight of the 15 girls is 40 kg. What is the average weight of the whole class?

Explanation

1. 01

   Total weight = $25 \times 48 + 15 \times 40 = 1{,}200 + 600 = 1{,}800$ kg.

2. 02

   Number of students = 40.

3. 03

   Average = $\frac{1800}{40} = 45$ kg.