One Teacher Retires and in Place of him a New Teacher 25 years Old joins :
Answer: (2) 55
The total numbers of teachers of a school = 10
One teacher retires and in place of him a new teacher 25 years old joins.
Then, the average age of teachers reduces by 3 years.
Therefore, the age of retired teacher = 25 + 3 x 10
= 25 + 30
= 55 years
Hence, the answer is (2) 55.