Question

The average age of 30 boys of a class is equal to 14 years. When the age of the class teacher is included the average becomes 15 years. Find the age of the class teacher?​

Answer 1

Answer:

average age of 30 boys = 14

sum of obv= n × average

14×30=sum of observation

=420

when teacher is included

n = 30+1=31

average=15

new sum = 15×31

new sum= 465

teacher age = 465-420

=45

Answer 2

Answer:

Therefore, class teacher's age = 30

Step-by-step explanation:

$\sf Mean = \frac{Sum \: of \: all \: observation}{No. \: of \: observation}$

$\sf \: \: \: \: \: \: \: \: \: \: \: \: = \frac{14 \times 30}{30} = \frac{420}{30} = \frac{42}{3}$

$\sf \: \: \: \: \: \: \: \: \: \: \: \: \: =14$

Now, they are asking when the mean (average) is 15 you have to find the class teacher's age.

$\sf \: \: \: \: \: \: \: = 14 + 1 = 15$

$\sf 15 \times 30 = 450$

Now, subtract it

$\sf 450 - 420 = 30$