A foolish incident

You know i was famous among classmates for asking doubts!! I could still remember, one day i asked my maths professor a doubt, he rubbed all the steps and wrote new steps on the board , but he was unsuccessful in solving it eventhough he spent half an hour! He started thinking and proved that my doubt was a rubbish!!!!!!!! All my great great classmates couldn't control themself..they made such a laugh that i will never forget... When everythng was over bell rang and few of my friends came to me and started praising me....for wasting the time of professor and saving them!