Question

The average age of a class of 39 students is 15 years. If the age of the teacher be included, then the average increases by 3 months. Find the age of the teacher.

• A. \( 20 \)
• B. \( 25 \)
• C. \( 35 \)
• D. \( 30 \)
• E.

Hint:

For average age problems, use the formula for the total age of all persons and subtract the total age of students to find the teacher's age.

Answer 1

The Correct Option is B

The combined age of the 39 students is calculated as: \[ 39 \times 15 = 585 \text{ years} \] After adding the teacher, the total number of individuals becomes 40, and the new average age is: \[ 15 + \frac{3}{12} = 15.25 \text{ years} \] The total age of all 40 individuals is then: \[ 40 \times 15.25 = 610 \text{ years} \] To find the teacher's age: \[ 610 - 585 = 25 \] Thus, the teacher's age is 25 years.