Still Okay With Your Maths?

Dear students / readers,

After having a long school break, why don’t you try this maths brain teaser 🙂

Football matches are to be organized in a round-robin format (each participating team plays a match against every other team only once).  If 21 matches are totally played, how many teams participated?  

Dalam satu pertandingan bola sepak yang diadakan secara round-robin (satu pasukan perlu melawan setiap pasukan lain hanya sekali sahaja).  Jika 21 jumlah perlawanan telah diadakan dalam pertandingan ini, berapakah jumlah pasukan yang mengambil bahagian?

Is anyone interested to try? The calculation is simple, but it really needs logical thinking 🙂



Posted on January 12, 2010, in Info Matematik. Bookmark the permalink. 7 Comments.

  1. i think its 7!

  2. Hi teacher! After calculating, i can get the answer, there is 7 teams playing. It’s all menatal and logic =P

  3. Ya, true. The answer is 7 🙂 . Quite easy ya?

  4. how to get 7??? got 3 only….

    • Dear lin,

      If 7 teams participated, the first team plays matches against the other 6 teams. The second team has already played against the first team, so that second team has to play matches against only the other 5 teams. In this manner, the second-last team has to play against only one team, and the last team has already played against all the teams. Therefore, the total number of matches is 6+5+4+3+2+1+0 = 21 matches 🙂

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