Bunuel wrote:
The average weight of 39 students is 38 kg. By the admission of a new student, the average weight is reduced to 37.5 kg. The weight of the new student is
A. 18 kg
B. 19 kg
C. 21 kg
D. 22 kg
E. 37.5 kg
The average weight of 39 students is 38 kg.So, we can write: (
sum of the original 39 students)/39 = 38
Multiply both sides of the equation by 39 to get:
sum of the original 39 students = (38)(39) = 1482By the admission of a new student, the average weight is reduced to 37.5 kg.So, we can write: (
sum of the 40 students)/40 = 37.5
Multiply both sides of the equation by 40 to get:
sum of the 40 students = (37.5)(40) = 1500The weight of the new student isWeight of new student =
sum of the 40 students -
sum of the original 39 students (since the difference in weight is due to the addition of the 40th student)=
1500 -
1482= 18
Answer: A
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