Question

The average age of a class of 23 students is 19 years. After a week, 7 students, whose average age is 21 years, joined the class. Later, 3 students, whose

average age is 18 years, moved to another class. What is the current average age of the class?
a. 19.6 years
b. 18.5 years
c. 20.1 years
d. 20.6 years

Answer 1

....sum of the ages of the initial class: 19*23=437

After a week, 7 students, whose average age is 21, joined the class.

sum of the ages of these students: 21*7=147

new sum of ages: 437+147=584

Later, 3 students, whose average age is 18, moved to another class.

sum of the ages of these 3 students: 3*18=54

sum of the ages of the pupils present in the class: 584-54=530

number of students present in the class: 23+7-3=27

the average age of this class is calculated:

= 530/27 ≈ 19.63 years ≈ 19.6

the current class average age is ≈19.6.