The average age of 25 students in a class is 12 years. 15 students whose average age is 10 years joined them. What is the present average age.	Answers
A) 13
B) 12.6
C) 11.25
D) 12
E) 13
Explanation :   Solution: Present average = ax + by/ a + b   = 25*12 + 15*10/25+15 years   =300 + 150/ 40 =&gt; 450/40 =&gt; 11.25.   Answer : 11.25
<result>C</result>
The average age of 25 students in a class is 12 years. 15 students whose average age is 10 years joined them. What is the present average age.