The mean weight of a class of 36 students is 41 kg. If one of the students leaves the class then the mean is decreased by 200 g.

Mean weight of 36 students = 41 kg

Sum of the weights of 36 students $=(41 \times 36) \mathrm{kg}=1476 \mathrm{~kg}$

Decrease in the mean when one of the students left the class = 200 g = 0.2 kg
Mean weight of 35 students = (41 -">−- 0.2) kg = 40.8 kg
Now,
Let the weight of the student who left the class be x kg.

Thus, we have:

$\frac{\text { Sum of the weights of } 36 \text { students }-x}{35}=40.8$

$\Rightarrow \frac{1476-x}{35}=40.8$

$\Rightarrow 1476-x=1428$

$\Rightarrow x=48$

Hence, the weight of the student who left the class is 48 kg.