Question

The average age of 30 students in a class is 18 yeras. When teacher's age is included to it, the average beocmes 19 years. What is the age of teacher?

Answer 1

Teacher's age

$$

\begin{array}{l}

=(31 \times 19)-(30 \times 18) \\

=589-540 \\

=49 \text { years; Ans. }

\end{array}

$$

---

Trick:

Teacher's age

$$

\begin{array}{l}

=18+\frac{30+1}{1} \times(19-18) \\

=18+31 \times 1 \\

=49 \text { years; Ans. }

\end{array}

$$