The average age of a class of 30 students is 15 years. If the teacher's age is included, the average age increases by 1 year. What is the teacher's age?
Answer and explanation
Correct answer: A. 46 years
- Step 1: Calculate the initial sum of ages of the 30 students: .
- Step 2: When the teacher joins, there are 31 individuals and the new average is . The new total age is . The teacher's age is the difference: .
Answer
46 years.
Why not the others: '42 years' assumes average increases by only 0.8; '' miscalculates as 494; '' adds an extra 2 years.
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