Question

the average age of 12 boys is 10 years if the average age of 11 boys is 9 years what will be the age of 12th boy ​

Answer 1

Answer:

average of 12 boys=

total age of 12 boys/ total boys

according to question ::--

total age of 12 boys = 12 × 10 = 120

total age of 11 boys = 11 × 9 = 99

we can write total age of 12 boys =

(age of 11 boys + age of 12th boy)

120 = 99 + age of 12th boy

age of 12th boy = 21

Answer 2

Answer:

Hope this answer might clear your doubt

Step-by-step explanation:

Average ages of 12 boys=10

Sum of observations =Average×No. of observations

=10×12

=120

Average ages of 11 boys=9

Sum of observations =Average×No. of observations

=9×11

=99

Age of 12th boy =120-99

=21 years

Hence age of the 12th boy is 21 years