The average age of a group of persons going for picnic is years. Eighteen new persons with an average age of 15 years join the group on the spot due to which their average age becomes 15.5 years. The number of persons initially going for picnic is	Choose the correct choice from the following:	A) 5	B) 10	C) 18	D) 32	E) 50
Solution   Let the initial number of persons be x. Then   16x + 18 x 15 = 15.5(x+20)   = 0.5x = 9   x =18.   Answer 18
<result>C</result>
The average age of a group of persons going for picnic is years. Eighteen new persons with an average age of 15 years join the group on the spot due to which their average age becomes 15.5 years. The number of persons initially going for picnic is