Question

the average age of child in a class of 35 is 11. the average age, including the teacher is 12. How old is the teacher?

Answer 1

47

Step-by-step explanation:

average = age/number of persons

1st case-

average = age of students/ no of students

11 = x/35

x1= 35*11= 385

2nd case

average = number of ages / number of people

12=x/36

x2=36*12=432

age of the teacher = x2-x1=432-385 = 47

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Answer 2

Given,

Students count in the class = 35

The average age of 35 students = 11

Average age including the teacher =12

To Find,

The age of the teacher.

Solution,

Total students count in the class N1 = 35

The average age of students Av1  = 11

Number including teacher N2 =36

The age average including teacher Av2 = 12

Let's find, the total age of the students.

Av1 =$\frac{total age1}{number of studenst}$

= $\frac{total age1 }{35}$

$\frac{total age1}{35}$ = 11

total age1 = 11 ×35

385.

Now, let's find the total age including the teacher.

Av2= $\frac{total age2}{number}$

12 = $\frac{total age2}{36}$

total age2 =12 ×36

432.

Teacher's age = total age2 -total age2

432 - 385 = 47.

The age of the teacher is 47.