The average age of a class of 30 students is 15 years. If the teacher's age is included, the average age becomes 16 years. What is the teacher's age?
Answer: B
Sum of ages of 30 students = 30 × 15 = 450 years.
When the teacher is included, there are 31 people and the average age is 16.
Sum of ages of 30 students + teacher = 31 × 16 = 496 years.
Teacher's age = 496 - 450 = 46 years.