10 बच्चो की औसत आयु 9 वर्ष 9, माह है। 9 बच्चो की औसत आयु 8 वर्ष 11 माह है,। दसवे बच्चे की आयु कितनी है ?

Options

A. 17 years 3 months
B. 18 years 4 months
C. 17 years 5 months
D. 18 years 3 months

Answer

A

Explanation

Average age of 10 children = 9 years 9 months
sum of ages of 10 children = `9 xx 10 + 9/12 xx 10`
`=390/4`
Average age of 9 children = 8 years 11 months
sum of age of 9 children = `8xx9 +11/12xx9`
`=321/4`
Age of 10th child = `390/4 - 321/4`
=`69/4` = 17 years 3 months