其它
Lucy, Maria and Anna have a meeting at $$12:30$$. Lucy\textquotesingle s walk takes $$10$$ minutes, Maria\textquotesingle s walk takes a quarter of an hour, and Anna\textquotesingle s walk takes $$40$$ minutes. At what time must the person who needs the longest time to get to the meeting leave her house? 
Overseas Competition->Knowledge Point->Combinatorics->Time Problem->Time Calculation
$12:30$ - $40$ min = $11:50$ 