Question

The average age of 30 students is 12 years. If the teacher's age is included, the average rises by 1 year. The teacher's age is:

• A. 43 years
• B. 42 years
• C. 40 years
• D. 31 years

Answer 1

The Correct Option is A

Step 1: Sum of students' ages \(= 30\times12 = 360\).
Step 2: With the teacher, 31 people average 13: total \(= 31\times13 = 403\).
Step 3: Teacher's age \(= 403 - 360 = 43\).

Quick Tip: A newcomer's value = new total minus old total.