Question

The average weight of a class of 39 students is 40 kg. When a new student is admitted to the class, the average decreases by 200 g. Find the weight of the new student.

Answer 1

ANSWER:
Average weight of 39 students = 40 kg
Sum of the weights of 39 students = 40×39 kg=1560 kg
Decrease in the average when new student is admitted in the class = 200 g = 0.2 kg
∴ New average weight = (40 - 0.2) kg = 39.8 kg
Now,
Let the weight of the new student be x kg.
Thus, we have:

Sum of the weights of 39 students+x/40=39.8
⇒1560+x/40=39.8⇒1560+x=1592⇒x=32
Therefore, the weight of the new student is 32 kg.