If: 2 = 6 3 = 12 4 = 20 5 = 30 6 = 42 Then: 9 = ?
The logical course of action (though in a moment I’ll show why it’s actually not) is to look for a pattern, right? And if we look at the numbers on the right we see that every time the number on the left is multiplied with a number one value higher: 2×3=6, 3×4=12, 4×5=20, 5×6=30, 6×7=42. This gives us the formula or , and if then the answer is 90. This is surely the most mathematical approach and pretty much refutes all the other possible answers.
Some people claim it’s 72, and they vehemently defend that answer. They claim if you follow the pattern, 4x5=20, 5x6=30, 6x7=42, then 9 must be multiplied by 8 to give 72. They are making the argument that one cannot assume the presence of 7 and 8 in the left-hand column and if 6 is multiplied by 7 then the next number, 9, must be multiplied by 8. It’s a reasonable argument, but not as convincing as the first one if you understand anything about number sequences.
The third most common answer is 56. These guys focused on the right-hand column. 6+6=12, 12+8=20, 20+10=30, 30+12=42. With every new line the number added increases by a value of two, so to 42 we must add 14 giving us 56. The big problem with this one is of course that it completely disregards the left-hand side of the equation which is a transgression of a central principle of arithmetic – two sides of an equation should always be in perfect balance.
Then there’s the bunch who insist the answer is 54 after they multiply 9 with 6, the number that appears before it in the puzzle. This solution does not follow any type of pattern whatsoever, nor does any of the other answers supplied.
The thing is, one version of the puzzle claims ninety percent of people will get it wrong, and as more than 50% of people say it’s ninety, there must be some trick to this, right?
I believe there is. I believe none of these answers are correct, not even 90, and it all comes down to one little symbol. Visit Page 3 below for my answer.