1 Answers
Option 5 : 20
Average = (sum of elements)/(number of elements)
Let the number of students initially in the nursery class be N.
Given,
The average age of a nursery class is 3 years -
The total sum of ages of all students in the nursery class
= 3N
Given,
10 new students with an average age 2.5 years are included in the same nursery class
Total sum of ages of 10 new students = 10 × 2.5 = 25 years
The total sum of ages of all students including new students
= 3N + 25
The average age of a class with new students = 17/6
⇒ 17/6 = (3N + 25/(N + 10)
⇒ 17(N + 10) = 6(3N + 25)
⇒ 17N + 170 = 18N + 150
⇒ N = 20
∴ Number of students initially in the nursery class is 20
There will be no change in the average 3 years after half semester there is no special condition provided for it. So the average will be 3 before 10 new students join the class.