The average weight of 40 students in a class is 55 kg. Six students of them whose average weight is 52 kg leave the class and another group…

Solution
Total weight of original 40 students = $40 \times 55 = 2200$ kg
Weight of 6 students who left = $6 \times 52 = 312$ kg
Weight of 6 new students who joined = $6 \times 42 = 252$ kg
=> New weight of new group of 40 students = $(2200 - 312 + 252)$ kg
= $2140$ kg
$\therefore$ Required Average = $\frac{2140}{40}$
= $53.5$ kg

Solution
Total weight of original 40 students = $40 \times 55 = 2200$ kg
Weight of 6 students who left = $6 \times 52 = 312$ kg
Weight of 6 new students who joined = $6 \times 42 = 252$ kg
=> New weight of new group of 40 students = $(2200 - 312 + 252)$ kg
= $2140$ kg
$\therefore$ Required Average = $\frac{2140}{40}$
= $53.5$ kg

The average weight of 29 students in a class is 54 kg. Five students of average weight 52.8 kg leave the class and 6 students of average weight 55 kg join the class, what is the average weight (in kg) of students now?