99.9% of people get this problem wrong

I saw this problem doing the rounds on LinkedIn, and wanted to see how my followers did with it. It’s a simple maths problem:


Anyone care to try?

If it makes you feel better, I got it wrong the first time!


51 thoughts on “99.9% of people get this problem wrong

  1. 200 I thought at first … if the first number is x then the second number is x * 2x

    But I’m going for 116, since you’ve said 3=18 and 7=98

    OR 100, since you said 5=50

    OR 104, since you said 4=32 and 6=72


    Don Charisma
    Don Charisma

  2. As a maths idiot (that is I am useless with numbers) I’m thinking 3 x 6 = 18 and 4×8 = 32 5 x 10 = 50 6 x 12 = 72 etc so 10 x 20 = 200 but then what do I know? I’m rubbish at numbers.

      • Sure, I will take a stab at it. I got the first answer wrong because I am an idiot, but that has never stopped me before.
        The problem is very vague, and as was said, 10 is really the only answer, unless we are talking about a structure, and scaling that structure on both sides of the equation.
        So 4 events at a certain magnitude (4/x)is equal to 32 (32/y)events at a very much higher magnitude. In other words, 4/x=32/y, which events/magnitude is the exponent that represents the structure in the Power law in the distribution of energy.
        You then have one sentence with two unknowns.
        To solve a sentence with two unknowns you need the two unknowns as variables in two solvable equations. So now all I need is the two sentences.
        I wouldn’t want to embarrass anyone by coming up with those sentences. It’s just not my style 🙂

      • The point of my question based on the above problem, is how would go about determine what my particular solution to the problem is, with the information given. I am not saying I have the one and only solution, there are many possible solutions. However how do you go about determine what my particular rule/pattern is.

      • Well Stephen, first I would have to get inside your observation, orientation, decision and action loop (OODA loop) to look at the problem the way you do.

        The OODA loop is a form of narrative decision making, so one way of getting inside your “loop” is to become a part of your narrative.

        So far, in that narrative, I have found that you get satisfaction from computers and you enjoy knowing something nobody else knows.

        I have joined that narrative by revealing to you that I get some kind of satisfaction from physics and I don’t enjoy secrets at all.

        The point of my first reply was: eventually I plan (if I continue this narrative) for you to have such an urge to tell me your “secret” (as I reveal to you that I don’t enjoy secrets) that you will have no choice but to overcome the urge for secrecy and you will tell me everything 🙂

      • Guys, before you two get too excited, might I suggest you continue your discussion on Steve’s twitter account – badbud65.

        Good luck trying to work out Steve’s algorithm.

      • After looking at his twitter account, the reason I would not continue this discussion on Steve’s twitter account is this. Like context-driven testing, when entering another’s OODA loop through a narrative it is better to enter at the narrowest position possible. It gives the testor and testie the least amount of room to maneuver as possible.

      • Hi larrydunbar, if you would like to do the challenge here is some context.

        The question as posted is for you to solve the pattern for what 10=’s. You can ask me any question you like. Some I will answer, but if asked what does 10= I will decline answering. Sometimes asking questions that give you a yes/no answer can help structure your approach. The challenge will be dealt with in a Socratic manner to challenge your critical thinking. This can sound rude. If at any time you don’t like the tone just say and be specific. If you’re not clear on an answer just ask for it to be rephrased. The idea is not really about solving it. The idea of a challenge is to spark critical thinking and for you to devise as many different ways as you can to try and solve the problem by deducing what the pattern is not. The experience is what is most important and what you learn not just the solution

      • From your answer to the tweet I posted, or the lack of an answer, I believe the answer to your question of what does 10 equal is zero.

        I also took in the fact that my tweet may have not reached you, as I didn’t follow your tweet account and I am not sure messages work the same between account that each don’t follow.

        My question in the tweet was: what in your personality makes you unable to accept 200 as the answer? By asking that question, even if it was not yours to answer, I must have believed that there was something in your personality that would give me the answer to your question. I think that “something” is control.

        There is something in your personality that you need to have control in every situation, including posting on this feed, as it seems to me like you tried to pretty much take control even when asked to take it else where.

        So I must have believe the pattern you followed, in reaching your answer involved eliminating all the tens and taking complete control.

        As you said, (“The idea of a challenge is to spark critical thinking and for you to devise as many different ways as you can to try and solve the problem by deducing what the pattern is not.”), or what is not “10”.

        So you took out 3 and 7, 4 and 6 on one side of the equal signs; then 1 and 9, 3 and 7, 8 and 2, 2 and 8 on the other side of the equals.

        In that pattern, you then reached across the equal sign and eliminated 5 and 5.

        What you had left was a single zero of the once mighty 50, and that was the answer.

        In other words, you took complete control of the situation, found what 10 in the pattern was not, and arrived at zero for your answer and effort.

  3. I will be assuming they are using the relation operator for assignment rather than equality, as the former has more interesting consequences.

    With a little effort we can come up with say,
    (-(1/30))n^5+(5/6)n^4-(49/6)n^3+(247/6)n^2-(459/5)n+84 which results in,
    18, 32, 50, 72, 98, 124, 138, 116, . . . .
    2n^2 gives
    18, 32, 50, 72, 98, 128, 162, 200, . . . .
    (The popular choice)
    n^5-25n^4+245n^3-1173n^2+2754n-2520 gives
    18, 32, 50, 72, 98, 248, 882, 2720, . . . .
    But then there is,
    (8/5)n^5-40n^4+392n^3-1878n^2+(22032/5)n-4032 that gives
    18, 32, 50, 72, 98, 320, 1314, 4232, . . . .
    And then there is ….
    … I can keep going all day, but I’ll just stop there.
    All these work, take your pick 🙂
    Finally, the point also is that given any finite set of numbers, the set does not necessarily define any single sequence.

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