Out of 10 teachers of a school, one teacher retires and in place of him a new teacher 25 years old joins. As a result of it average age of the teachers reduces by 3 yrs. Age of the retired teacher is:
Answer & explanation
Correct answer: option 1
Average of 10 teachers decreased by = 3 years and
Total age of 10 teachers decreased by = 10 × 3= 30 years
It means the new teacher's age is 30 years less then the teacher who retired.
Hence, The age of teacher who retired is 25+ 30 = 55 years.
OR
Let initial average be ‘x’
Age of all teachers = 10x
New teacher age = 25
Let retired teacher age = y yrs
New average = x – 3
\(\frac{10x+25-y}{10}\) = x – 3
10x + 25 – y = 10x – 30
y = 55 yrs.