A family has several children. Each boy in the family has as many sisters as brothers and each girl has twice as many brothers as sisters.. How many brothers and sisters are there?
(a)4 brothers, 3 sisters
(b)4 brothers, 4 sisters
(c)3 brothers, 4 sisters
(d)Cannot say
Answer
Answer (as printed): A
Explanation
Let the number of boys in the family be $x$. Then each boy has $(x-1)$ brothers and $(x-1)$ sisters. So, number of girls $=(x-1)$. Thus each girl has $x$ brothers and $(x-2)$ sisters. $\therefore \quad x=2(x-2) \Leftrightarrow x=2 x-4 \Leftrightarrow x=4$. So, there are 4 boys and 3 girls i.e., 4 brothers and 3 sisters in the family.
Explanation as extracted from the printed page; notation may be imperfect.