Question

The average age of 30 students in a class is 12 years. The average age of a group of 5 of the students is 10 years and that of another group of 5 of them is 14 years. The average age of the remaining students is

• A. 8 years
• B. 10 years
• C. 12 years
• D. 14 years

Answer 1

Answer: (C)

12 years

Average age of 30 students in a class = 12 years
5 students = 10 years
Another 5 students = 14 years
remaining student= 30-5-5=20
let's assume average age of 20 student=x
Total age of all student=average age* total no of student
$30\ast 12=5\ast 10+5\ast 14+20\ast x$
$360=50+70+20x$
$360=120+20x$
$240=20x$
$x=12$
Answer (C) 12 Years