Stumped by Primary One Math

Athos had some math homework over the weekend and was having difficulty with one question in particular. “Come, I’ll help you,” I said, beaming with motherly love and teacherly wisdom, all prepared to gently guide him towards the solution.

10 minutes later, I was practically foaming at the mouth, convinced that either there was a typo in the assignment in which case someone ought to be shot for wasting my time, or that our education system was perverse for pitching so high that something that ought to be fun became a destroyer of self-esteem (mine, never mind Athos!)

I’ve since regained my composure. As well as figured out the answer.

See if you can too!

Look at the following series of numbers. What number does the question mark represent?

1 9 2 ? 3 7 8



17 responses to “Stumped by Primary One Math

  1. Is the answer “5”? My self-esteem at stake

  2. Well done, spots 🙂 Of course, Athos has yet to get his homework back, so let’s see if we’re both right, or out-done!

  3. Actually I still feel a typo would make more sense!

  4. Boy, this is logic but really “chim”. Sophie guessed “5”. So she is on the same note. As for me, it did not make immediate sense until I saw the answer and worked backwards and surmised it is ‘5’.

  5. ok, now i’m really afraid to bring my kid back to singapore….what is this stuff? things were much much easier when I was in Pri 1, and I would like to think that I turned out fine mathematically! HELP!!!

  6. I have to say I am embarrassed. I’ve been looking at this, and I still could not get it.
    How do we get ‘5’?

  7. Thanks for all the responses and I’m glad I’m not alone! May, how we got at the answer was to start at 1 and spiral inwards. So 1 + 8 = 9; 9 – 7 = 2; 2 +3 = 5.

  8. I refuse to get sucked into this madness 🙂
    Today, I took a mental health break. I just couldn’t handle Mag’s Primary 2 math exercises anymore. We were both going crazy.

    And while you’re tackling this in Singapore, read what’s happening here on the other extreme:
    They’re thinking of banning homework.

  9. Thanks, Pilgram Mom. I agree with John on the ‘chim’ part.

    I am really not sure if difficult questions are given, just for it’s own sake, without regarding the real key Maths principles of what a P1 kid should grasp.


  10. This is bad, I had to look at the answer to solve it 😦 So much for getting A’s at O levels A-maths and E-maths… guess I’ve been deluded.

    Though I agree with E and feel that a typo (get rid of the final digit ‘8’) might make more sense, then the ? would be 8 and with a lot more logic because usually one would go into a problem like this thinking there is continuity in the pattern.

  11. I am still wondering whether there is any useful value in this particular Maths problem for a Pri 1 kid. The other day, as I was driving Athos home, I asked him whther he understood the sum [ after you have all figured out the answer].
    He said ,” nope!”
    I figured that was just about the only correct response too.

  12. yikes. I don’t think this makes sense at all. Why is it a pattern if you have to spiral inwards, changing from plus to minus!? I think it is time for me to migrate!

  13. Pingback: Pri 1 Math « M

  14. My Pri 6 brother solved it with ‘5’ but his logic was:

    1+9 = 2 x5
    5 x 3 = 7+8

    Does that make more sense?!

  15. 526, that is the cheemest solution I’ve seen. It makes sense but probably not what this question calls for because they haven’t learnt multiplication.


  16. Like most of you, I was surprised that this was a Pri 1 question. So I tried not to think too ‘chim’ to obtain the answer. My answer was ’10’.

    First reason: I looked at the set as 5 digits (1,9,2,?,3) followed by 8,7. I then tried to get a pattern such that the set gives an 8, followed by a 7. Hence 9-1=8 and 9-2=7. The pattern will then be 10-2=8 and 10-3=7.

    2nd Reason: I was told by my cousin that the answer was ‘5’ and not ’10’. I was not satisfied and re-looked again. This time I looked for a pattern to cover the full set of digits. I put the set of numbers in groups of 3 digits; 1, 9,2; 2,?,3; 3,8,7. Summing each group up gave 12; 2,?,3 and 18. Hence if you use ’10’, it would give a sum of 15. The pattern would then be a difference of 3 between the sum of each group, i.e. 12, 15, 18 {1,9,2,10,3,8,7}

    If the answer is ‘5’, it’s hard to get a consistent pattern and difficult to explain why we add 3 and not any other numbers to the 2 to get 5. Also, it does not explain the pattern for obtaining the numbers 3,8,7 or how it is linked with the pattern of adding 8 and subtracting 7.

  17. Yeah we just checked with my mum who said pri 1 wouldn’t have learnt multiplication in term 1.

    And I should have added that this little brother of mine is going for maths olympiad so he die-die also will create a solution even if there is none, ha!

    He also said something along the lines of why must it be 2+3 instead of 2-3 (which gives -1 which obviously primary 1 won’t even realise its existence) or 2×3 (again, no multiplication yet) or 2/3 (ok forget it, he has forgotten that we have to be thinking like a primary 1).

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