Question

In a school, the average age of boys and girls together is 16.8 years, the average age of boys is 15.4 years, and the average age of girls is 18.2 years. The ratio of number of boys to girls in the school is:
1. 3 : 2
2. 3 : 5 
3. 2 : 3
4. 1 : 1

Answer 1

Correct Answer - Option 4 : 1 : 1

Given:

Average age of (Boys + Girls) = 16.8 years

Average age of boys = 15.4 years 

Average age of girls = 18.2 years

Formula used:

By Alligation Method

Average (B)                                                               Average (G) 

                                   Average ( B + G)

(G) - (B + G)                         :                                    (B + G) - B       [Ratio of no boys and girls]

Calculation:

15.4                                                                               18.2 

                                         16.8 

(18.2 - 16.8)                        :                                    (16.8 - 15.4)

1.4                                       :                                         1.4 

∴ The required ratio of number of boys to girls is 1 : 1.