The average age of a class of 30 students is 12 years. If the average age of 5 of these students is 10 years and another group of 5 is 14 years, then the average age of the remaining students is:

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 x total no of student

$\mathrm{30\; x}12=\mathrm{5\; x}10+\mathrm{5\; x}14+\mathrm{20\; x\; X}$

$360=50+70+\mathrm{20X}$

$360=120+\mathrm{20X}$

$240=\mathrm{20X}$

$X\; =\mathrm{12years}$