Please enjoy this brain teaser compliments of puzzle master Wes Carroll. He found this one in the Mensa publication Number Puzzles for Math Geniuses by Harold Gale.

The Empty Triangle

The Empty Triangle

Question:
Which figure should be placed in the empty triangle?

This puzzle works your executive functions in your frontal lobes by using your pattern recognition, hypothesis testing, and logic. Let us know how you do!

Click here to read the Answer and Solution.

17 Responses to “Pattern Recognition Brain Teaser - The Empty Triangle”
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  2. kevinon 15 Jul 2007 at 9:28

    adding across, the number in the top row equal 26, the numbers in the bottom row equal 26, so the number in the empty triangle should be 6 so that row can also equal 26

  3. robon 20 Aug 2007 at 7:15

    i came up with the same answer as kevin the sums added across all equal 26 if 6 is placed in the triangle.

  4. Toffeeon 23 Aug 2007 at 9:40

    Another option if you look at it as a set...
    (6-2)+ (6-2) = 8
    (7-5) +(7-3) = 6

    For the third one and fourth as a set follow the same rule

    (7+4)- (7-2)= 6
    Therefore
    (6+5) - (6-3) = 8

  5. [...] 16. Find the missing number in The Empty Triangle. [...]

  6. Dan Bowleson 17 Oct 2007 at 1:36

    Right answer first time! :)

    The key to the problem is that it is pattern recognition - that is that each triangle is a distinct event.

  7. davidon 17 Oct 2007 at 2:05

    The correct answer is 3...

    #1 (6-2)*2=8
    #2 (7-5)*3=6
    #3 (7-4)*2=6
    #4 (6-5)*3=

  8. NightLordon 28 Nov 2007 at 2:04

    I got 8.
    First triangle total is 18.
    Second triangle is 21.
    Third triangle is 19.
    This, with a skipping pattern the fourth triangle should jump to 22.
    Thus, 8 in the last triangle.

  9. Yomandaon 29 Nov 2007 at 4:12

    3. fo sho.

  10. zedaon 17 Jan 2008 at 10:40

    (6*2)-(2*2)= 8
    (7*3)-(5*3)= 6
    (7*2)-(4*2)= 6
    (6*3)-(5*3)= 3

    I mulitiplied the top number with the bottom right numbe. Then multiplied the bottom two numbers and subtracted the two totals. Guess i took the longer route!

  11. yahobahneon 20 Jan 2008 at 9:10

    i say 7 is the missing number
    pattern: 18,21,19,21...
    21 is the constant number while the others decrease by one

  12. siobhanon 24 Jan 2008 at 11:17

    The answer is 3.

    6-2=4*2=8
    7-5=2*3=6
    7-4=3*2=6
    6-5=1*3=3

  13. Aaronon 23 Mar 2008 at 10:22

    I got 8, just because it goes "6, 7, 7, 6" on top, then "8, 6, 6, X" in the triangle, so the pattern would make sense if it were 8.

  14. sudhasinion 08 Apr 2008 at 4:23

    answer is 3

    IN first traingle 8/2=4
    add 2 with 4 =6.
    IN second one
    6/3=2+5=7
    IN 3rd triangle
    6/2=3+4=7
    IN 4th triangle
    3/3=1+5=6

  15. Richardon 09 May 2008 at 9:13

    Answer to

    1 3 5 7 9 R
    whelmint

  16. Lmnopon 18 Jun 2008 at 4:41

    I haven't checked the answer yet, but I'm going to go ahead and say that it's 3.

  17. Lmnopon 18 Jun 2008 at 4:44

    After checking the way you were "supposed" to get to the answer, I found out I did it the "wrong" way. I did it the same way as zeda. I suppose the other way would have been quicker; oh well.

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