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

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.


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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
i came up with the same answer as kevin the sums added across all equal 26 if 6 is placed in the triangle.
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
[...] 16. Find the missing number in The Empty Triangle. [...]
Right answer first time!
The key to the problem is that it is pattern recognition - that is that each triangle is a distinct event.
The correct answer is 3...
#1 (6-2)*2=8
#2 (7-5)*3=6
#3 (7-4)*2=6
#4 (6-5)*3=
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.
3. fo sho.
(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!
i say 7 is the missing number
pattern: 18,21,19,21...
21 is the constant number while the others decrease by one
The answer is 3.
6-2=4*2=8
7-5=2*3=6
7-4=3*2=6
6-5=1*3=3
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.
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
Answer to
1 3 5 7 9 R
whelmint
I haven't checked the answer yet, but I'm going to go ahead and say that it's 3.
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.