This is an IQ test I found recently. What is the number in the square with "?"? I have thought it for a long time but cannot know the answer. Does anybody know the answer and the reason? Thanks in advance.
4 Answers
98
Reason
flipped first column = middle column - last column
eg:
flipping 65, 56 = 69 - 13 flipping 14, 41 = 63 - 22Hence ? will be 98
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2$\begingroup$ I believe that you mean "flipped first COLUMN = middle COLUMN − last COLUMN." P.S. As long as you're putting the answer in a spoiler block, do so consistently. $\endgroup$ May 23, 2016 at 6:52
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1$\begingroup$ Oops, Its column, thanks for the edit and suggestions :) $\endgroup$– renjiMay 23, 2016 at 7:04
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1
The answer is:
$78$
The reason is:
If row elements are $a_1$, $a_2$ and $a_3$ from left to right: $$a_2 = (-35a_1 - 247a_3 + 10523) / 73$$ $69 = (-35 * 65 - 247 * 13 + 10523) / 73$
$63 = (-35 * 14 - 247 * 22 + 10523) / 73$
So the answer should be: $$(-35 * 18 - 247 * 17 + 10523) / 73$$
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3$\begingroup$ You could do this for any possible answer, because there are three parameters (two coefficients and the constant term) and only two constraints. $\endgroup$– f''May 23, 2016 at 7:54
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3$\begingroup$ My plan was to say all four answers are correct. Then I got bored in proving first answer is correct. In short I don't find such questions appealing. $\endgroup$ May 23, 2016 at 8:07
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3$\begingroup$ @MohitJain I think that the purpose of this kind of "IQ test " question is to find a solution as short and natural as possible $\endgroup$– FabichMay 23, 2016 at 10:07
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1$\begingroup$ @Lordofdark You are right. I lost the spirit a little early :( $\endgroup$ May 23, 2016 at 12:06
I got the correct answer, but I did it a different way
Answer
98
My solution
The sum of the ones place digit in column one and the tens place digit in column three equals the tens place digit in column two, the sum of the tens place digit in column one and the ones place digit in column three equals the ones place digit in column two soo...
65 69 13 -- [5 + 1][6 +3] -- [6][9] = 69
14 63 22 -- [4 + 2][1 +2] -- [6][3] = 63
18 ?? 17 -- [8 + 1][1 +7] -- [9][8] = 98
?
: the square has a?
. The question "which number should replace the?
?" might have a different answer. :) $\endgroup$