The three college students who won TD Ameritrade's annual thinkorswim challenge - a virtual stock market game - saw portfolio gains of 427% in just one month.

"The thinkorswim Challenge is an amazing opportunity for a younger generation to learn about investing through practical application," said Lee McAdoo, managing director of education at TD Ameritrade. 

For the second straight year, students in the challenge focused on technology trades, such as Tesla (TSLA - Get Report) , Apple (AAPL - Get Report) and Amazon (AMZN - Get Report) .

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