Typo in this one lol 9 * 8 + 9 - 9 - 9 / 9 = 72 s/b 9 * 8 + 9 - 8 - 9 / 9 = 72 I used to know about quadratic equations and factoring but it all seems to be slipping away...lol
Very difficult IQ problem
- Thread starter stinkynuts
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This is the "correct" solution. You guys are right, there are other solutions possible, but this is the simplest solution.
I forgot to mention that this was a multiple choice problem. Theoretically, I'm sure that if you made the function convoluted enough with multiple operations, you could prove that the other answers were correct as well. But 80 is correct because it requires the fewest operations. I suppose I should have put that in my orignial problem (the fewest operations is the correct one).
Congrats to those who solved it, either method.
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Thank you stinky, that is indeed an original meaning for a conventional symbol which I never would have guessed. I was right, you were quite capable of mystifying me on your own. I think I get it now but it's certainly newer math than mine.
There are an infinite number of solutions, with the "correct" solution being the prettiest but not the simplist. If the function is of the form x@y=z, then the solution with the fewest coefficients (aka the simplist) is:
z = (9/8)*(x-1)*y = -(9/8)*x + (9/8)*x*y
Congrats to the people who said: 81.
The psychologically correct solution is:
z = (x-1)(y+1) = xy - y + x - 1
This yields: 80 as an answer. This solution looks pretty, and happens to resemble an elementary theorem. Although, it is a misquote of the theorem.
There are no solutions of the form: z = a + b*x + c*y, for any real numbers a,b and c. There are an infinite number of solutions of the form: z=a + b*x + c*y + d*x*y, for real a, b, c, and d, with c and d not equal to zero. I didn't bother analyzing the general 2nd order case with z=a+b*x+c*y+d*x^2+e*x*y+f*y^2, because a vast number of solutions are possible. Formally, a 2nd order solution would include all second order terms, meaning if the x^2 and y^2 should be included.
It makes sense this question came from an IQ test, because the answer is the psychologically correct answer and not the mathematically optimal answer.
Absolutely, or is just plan God awful at mathematics & algebra etc. . . it is interesting that when such questions are either the only ones counted or totally discarded the subjects supposed IQ can either go crashing through the ceiling or sink through the bottom.
I don't believe the solution you say is correct fits the original criteria in which two operands were to be combined with an arbitrary operation or operations. In the clarifying example it is shown that the operands can be repeated and more than one operation can be applied. In the solution accepted as correct a third operand is introduced. (The number 1)
The solution I came up with (subsequently factored down correctly by rhuarc29) has only the original two operands plus multiple operations...
Are you sure?
I could assume that 1 is zero like you did, but alternatively assume that 3 is 3, and 8 is 6, and 9 is 12 to make the first 3 answers 0, 18 (3 x 6) and 72 (12 x 6) too.
Therefore, 9 @ 9 is 12 x 12 = 144 and not 81.
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Then your question was not an IQ question but a stupid guessing game.
Sorry, but you wasted everybody's time.
IQ tests are a guessing game. The idea is to outguess the questioner.
If the question asked for the best fit 2nd-order function with the fewest non-zero coefficients to match the chosen data sample, then the answer would have a single mathematical solution. Only people that took the math courses required to understand the question would be able to find the solution.
Instead, the IQ test poses psychologically weighted pattern puzzles. The better answers are given higher point weights. Thus maximizing one's score on an IQ test involves guessing at which solutions are given the highest point weights. "Intelligent" people improve their IQ scores by taking multiple tests. It is possible to get better at solving the puzzles, guessing which solutions have the highest weights, and to achieve higher IQ scores.
sure, you could do that, you could even make 9 x 9 = a puppydog if you really wanted to. but why complicate things and make 3 assumptions like in your example? i just picked the easiest way i knew to get the answer, but adickson came up with an answer that makes only 1 assumption, so i guess he is more right. if i knew more math i would have gone with that answer as well.
I asked because 1 = 1 and 3 = 3.
1 is not 0 and 3 is not 2.25. Ever.
Therefore you must have had an inkling that your answer could not have been the correct one even though it "works".
There are various ways to look at this. A person may be 1) unable to solve the problem 2) able to solve the problem but only by changing the rules (in this case the fundamental principles of mathematics), and therefore would know that although the "obvious" answer "works" it cannot be the correct one 3) solve the problem with one solution 4) solve the problem in more than one way correctly.
As for "[knowing] more math", a correct answer for this particular problem only requires the test taker to be able to add, subtraction, and multiply - all of which are learned before or in 4th grade.
Therefore, the key to this question is less about "knowing math" and more about the test taker being able to problem solve.
With all that said, don't put much stock into the question. It's only one question and it doesn't define anybody's intelligence. I'm just pointing out that when you attempt to solve mathematical problems, you must do so using the laws of mathematics. If you don't, your answer is going to be wrong.
Not quite. Because he also forgot to include the multiple choices. But he did get responses and discussion, which is the point.
And will be more careful and complete next time. We hope.
