Subject: General Aptitude · Chapter: Ratio and Proportion · Exam: · Marks: · Difficulty:
How many boys are there in the class? (M.A.T., 2007) I. The class has 45 children in all and ratio of boys to girls is 4 : 5. II. The ratio of girls to boys is 4 : 5 and boys are nine more than the girls.
Answer
SELF-PRACTICE — the source book printed no answer.
Nothing is invented here, so this question has no answer on record.
Explanation
I. Let the number of boys and girls be $4x$ and $5x$ respectively. Then, $4x+5x=45 \Rightarrow 9x=45 \Rightarrow x=5$. $\therefore$ Number of boys $=(4\times5)=20$. II. Let the number of girls and boys be $4x$ and $5x$ respectively. Then, $5x-4x=9 \Rightarrow x=9$. $\therefore$ Number of boys $=(5\times9)=45$. Thus, either I alone or II alone gives the answer. $\therefore$ Correct answer is (c).
Explanation as extracted from the printed page; notation may be imperfect.