## Two Three Four Fifteen

What is the missing number?

2 3 4 15 12
3 4 5 28 20
4 5 6 45 30
5 6 7 66 42
6 7 8 ?? 56

91. To get the number in the fourth column, you add the numbers in column 1 and 2, then multiply by the number in column 2. f(n,m) = (n + m) * m
For example, f(2,3) = (2 + 3) * 3 = 15. Thus f(6,7) = (6 + 7) * 7 = 91

Posted in Brain Teasers
Tagged with

3 Comments on "Two Three Four Fifteen"

NEIL WILSON says
January 12, 2016 @ 01:35

91, the answer is acheived by adding the first two numbers together and multiplying by the second number.
i.e (2+3)x3=15, (3+4)x4=28 etc

Harm says
April 25, 2016 @ 04:19

Well, this one is a bit dubious. By dismissing columns 3 and 5, you can come up with plenty of different solutions. Like 67: there is a pattern in columns 4 and 5, column 5-4 = -3, -8, -15, -24. This has pattern +5, +7, +9, +11 so the next one is +11. And 56 + 11 = 67.

Ed says
April 13, 2017 @ 01:07

well i dont see any nines in there like at all
{"found_math": false, "script_math_tex": 0, "script_math_asciimath": 0, "math_annotations": 0, "math_alttext": 0, "mathml": 0, "mathjax_tag": 0, "mathjax_inline_tex": 0, "mathjax_display_tex": 0, "mathjax_asciimath": 0, "img_math": 0, "codecogs_latex": 0, "wp_latex": 0, "mimetex.cgi": 0, "/images/math/codecogs": 0, "mathtex.cgi": 0, "katex": 0, "math-container": 0, "wp-katex-eq": 0, "align": 0, "equation": 0, "x-ck12": 0, "texerror": 0}