The average age of a group of friends is 27 years. If 4 new friends whose average age is 25 years join them, the average age of the entire group becomes 26 years. How many people were there in the group initially?

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Answer (Detailed Solution Below)

Option 2 : 4
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Given:

The average age of a group of friends is 27 years.

If 4 new friends whose average age is 25 years join them, the average age of the entire group becomes 26 years.

Calculation:-

Let's denote the initial number of friends in the group as "N".

The sum of the ages of the initial N friends = 27N.

After 4 new friends join the group, the average age becomes 26 years.

Now, the total sum of ages of the entire group after the 4 new friends join,    

⇒ 26 (N + 4).

According to this question,

⇒  27N + 4 ×  25 = 26N + 104 

⇒ 27N + 100 = 26N + 104

⇒ N + 100 = 104

Subtract 100 from both sides: N = 4

∴ Initially, there were 4 friends in the group. 

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