The average age of 40 students of a class is 16 years. After admission of 10 new students to the class, the average becomes 15 yers. If the average age of 5 of the new students is 11 years, then the average age ( in year) of the remaining 5 new students is :
Show answer & explanation
Correct answer: C
Explanation
The correct answer is Option 3 i.e. 11.
We know that,
Average = Sum of observations/Number of observations
The sum of ages of 40 students = 40 × 16 = 640 years
After the admission of 10 new students,
Total number of students now = 40 + 10 = 50
The sum of all ages after the admission of 10 new students = 50 × 15 = 750 years
The sum of ages of 5 new students = 5 × 11 = 55 years
Now remaining ages of 5 new students = 750 - 640 - 55
⇒ 750 - 695 = 55 years
Average of 5 new students = 55/5 = 11