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A train was supposed to arrive at a $$MRT$$ station at $$5:30 \rm pm.$$ But the train arrived half an hour early because of a traffic accident and changed another line. What time did the train reach the $$MRT$$ station? (adapted from 2008 Math kangaroo Problems, Level 3-4 , Question \#6） 
Overseas Competition->Knowledge Point->Combinatorics->Time Problem->Time Calculation
$5:30$-$30$ minutes=$5:00$ 