Seattle Seventh Grader Wins National Math Bee (ap.org)

Edward Wan, a Seattle-based seventh grader has won the national math bee. Wan, who studies at Lakeside Middle School, beat 224 other middle school students nationwide to win the 2016 Raytheon Mathcounts National Competition. From an Associated Press report: Competition officials said in a news release the 13-year-old won the final round by answering the question, "What is the remainder when 999,999,999 is divided by 32?" Wan gave the correct answer of 31 In just under seven seconds.Deadspin reports about the live streaming of the event: Today's Mathcounts national championship for middle-school mathletes aired on ESPN3, and it was definitely the best live sports anyone could be watching at 10 a.m. on a Monday morning. We couldn't agree more.

Comments

Quick kid

[TheEmptySet]

Maths is about understanding something the right way. And I'm guessing this kid did not take the seven seconds to do anything complicated. He just factored 32. i.e. 2^5. Then noticed that 999,999,999 + 1 = 1,000,000,000 = 10^10 = 2^10 * 5*10 which clearly contains a factor of 2^5. So 32 goes into 1,000,000,000. So the remainder after division of 999,999,999 by 32 is 31. I think you need about 2 seconds for that once you realise the correct way to think about it. So he took 5 seconds to work out what he should do. Quick kid!

Solvable in 1 second.

[sconeu]

10^n is evenly divisible by 2^n

Therefore 999,999,999 = 10^9-1. Therefore the remainder is -1 mod 32 which = 31.