Competition problem — Algebra — Maths Olympiad Prep

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Algebra Difficulty 1.7 Junior Find the answer

The average age of $5$ people in a room is $30$ years. An $18$ -year-old person leaves
the room. What is the average age of the four remaining people?

Pick one

Solution

Let $x$ be the average of the remaining $4$ people.
The equation we get is $\frac{4x + 18}{5} = 30$
Simplify,
$4x + 18 = 150$
$4x = 132$
$x = 33$
Therefore, the answer is $\boxed{\textbf{(D)}\ 33}$

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