From a group of boys and girls, 15 girls leave. There are then left 2 boys for each girl. After this, 45 boys leave. There are then 5 girls for each boy. Find the number of girls in the beginning.
Answer
Answer (as printed):
Explanation
Let at present there be $x$ boys. Then, number of girls at present $=5 x$. Before the boys had left: Number of boys $=x+45$ and number of girls $=5 x$. $$\therefore \quad x+45=2 \times 5 x \Leftrightarrow 9 x=45 \Leftrightarrow x=5 .$$ Hence, number of girls in the beginning $=5 x+15=25+15=40$.
Explanation as extracted from the printed page; notation may be imperfect.