a) 28 years
b) 30 years
c) 33 years
d) 35 years
Answer: c
Explanation: Average of 20 students = 12 years
Total age of 20 students
= 20 × 12
= 240 years
When teacher included average become 13 years
Now, total age 20 students and teacher
= 13 × 21
= 273 years
∴ Age of teacher
= 273 – 240
= 33 years
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