2016 · Q40
If the mean age of combined group of boys and girls is 18 years and the mean of age of boys is 20 and that of girls is 16, then what is the percentage of boys in the group ?
Elementary MathematicsStatistics
- A60
- B50
- C45
- D40
Explanation
By alligation, the ratio boys:girls = (20−18):(18−16) = 2:2. Boys are therefore half the group, i.e. 50% (option B).