Question

The average age of 6 persons increases by 1.5 years when 3 new members joined the group whose average age is 18 years find the average age of the group initially

Answer 1

6x1.5 =9
total 9 members then average age is 18
so 18*9= 162
initially 153

Answer 2

SOLUTION:

Let the avg age six membeR (group) initially = x years.

∴ Total age of six person = 6x

Now, 3 memeber joined the group having age of 18 years each.

∴ Total age of 3 members = 18*3 =54 years

∴ Total age of 9 person = 6x+54 years

∴ Their average age = (6x+54)÷9 years

Since , the average age is increased by 1.5 years when 3 members joined the group.

∴ average age of 9 members = x + 1.5 years

THIS FORMS EQUATION

⇒ (6x+54)÷9 = x + 1.5

⇒ 6x+54 =9x+13.5 (cross multiplication)

⇒ 40.5 = 3x

⇒ x = 13.5

The average age of group initially = 13.5 years ANS.