In a class, the average weight of 40 boys is 65 kg and that of 50 girls is 60 kg. After a few days, 40% of the girls and 50% of the boys leave. What would be the new weight of the class (in kg)? Assume that the average weight of the boys and the girls remains constant throughout.
(a) 65
(b) 62
(c) 68 L
(d) 55
Sol:
60% girls = 30 × 60 = 1800 kg
50% boys = 20 × 65 = 1300 kg
Total = 3100 kgs
Averages=3100/50=62 kg