Question

The average age of 30 children in a class is 9 years .if the teacher's age is added the average age becomes 10 years what is the Teacher's age, in years

Answer 1

Given 30 students avg. age = 9 years.

So total age of 30 students = 9*30 = 270 years.

Teacher's age included.  

So, avg. of 30 students + one teacher = 10 years.

=> Total age of 30 students + one teacher = 10 * 31 = 310 years.  

Therefore age of teacher = (310-270) = 40 years.

Answer 2

Answer:

age of teacher = 40 years

step by step explanation :-

given -

average age of 30 children = 9 years

total age of 30 children = 30× 9

=270

average age including teacher

( 30 students + 1 teacher ) = 10

total age including teacher = 31× 10

=310

age of 30 students + age of teacher = 310

270+ age of teacher = 310

age of teacher = 310 - 270

=40