$2400\times2\div(53+47)=48$min 
The distance between the school and the park is $$2400$$ $\text{m}$. Lily and Candy depart from the school towards the park at the same time, and return immediately after arriving at the park. Lily travels $$47$$ $\text{m/min}$, and Candy travels $$53$$ $\text{m/min}$. They will meet each other for the first time after~\uline{~~~~~~~~~~}~minutes. 
[1] $$24$$ 
[2] $$48$$ 
[3] $$72$$ 
[4] $$96$$ 