Question

173. In a school there are 600 students. The average age of the boys is 12 years and that of
the girls is 11 years. If the average age of the school students is 11 years 9 months, then
find the number of boys in the school.​

Answer 1

Answer:the total number of girls in school is 150.

Total number of students in school = 600 (Given)

Average age of all students = 11 yrs 9 mnths (Given)

Average age of boys is 12 years (Given)

Average age of girls = 11 years (Given)

Let the number of girls be = x  

Total age of girls = 11x --- equation 1  

Number of boys = 600-x

Total age of boys = 12 ( 600-x) --- equation 2  

= 11 × 9/12 = 47/4 yr

Therefore, total age of all the students -  

= 600 × 47/4 = 7050 ---equation 3

From equation 1, 2 and 3  

11x + 12 ( 600-x) = 7050

11x + 7200 - 12x = 7050

11x-12x = 7050 - 7200

-x = - 150

x = 150

Step-by-step explanation: