Question

The mean weight of 25 students of a class is 48 kg. If the mean weight of first 13 students is 50 kg. and that of last 13 students is 46 kg. Find the weight of the 13^th student.

Answer 1

Mean weight of 25 students = 48 kg
∴ Sum of the weights of 25 students = 48$\times$25= 1200 kg
Now,
Mean weight of the first 13 students = 50 kg
∴ Sum of the weights of the first 13 students = 13$\times$50 = 650 kg
Also,
Mean weight of the last 13 students = 46 kg
∴ Sum of the weights of the last 13 students = 13$\times$46= 598 kg
Thus, we have:
Sum of the weights of the first 13 students and the last 13 students = 650 + 598 = 1248 kg
Weight of the 13th student = $1248-1200=48\mathrm{kg}$