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Math Challenge 2019

Discussion in 'Mathematics' started by Shin0bi3Z, Jul 2, 2019.

  1. Shin0bi3Z

    Shin0bi3Z New commenter

    How do you add up 27 and 48 in your head?
    In my head it looks like this:

    20 + 40 =60,
    60 + 7= 67,
    67 + 8= 75
  2. nervousned

    nervousned Senior commenter

    CHuynh and Shin0bi3Z like this.
  3. BG54

    BG54 Occasional commenter

    Column addition, identical to the way I do the calculation on paper.
    Shin0bi3Z likes this.
  4. teselectronic

    teselectronic Occasional commenter

    30 + 50 - 5 = 75
    yodaami2 and Shin0bi3Z like this.
  5. neddyfonk

    neddyfonk Lead commenter

    40 + 27 = 67
    67+8 = 75
    or computerwise - convert to binary
    11011 + 110000 = 1001011 = 64+8+2+1 = 75
    Could have been worse if I used hexadecimal.
    yodaami2 and Shin0bi3Z like this.
  6. NoSuchThingAsNormal

    NoSuchThingAsNormal New commenter

    60 + 15 = 75
    Shin0bi3Z likes this.
  7. Shin0bi3Z

    Shin0bi3Z New commenter

    I like your approach to the problem.
    yodaami2 likes this.
  8. Shin0bi3Z

    Shin0bi3Z New commenter

    That is cool, I never thought of solving it that way. That is illuminating! Great!
    You are right hexadecimal is a whole other beast.
  9. Shin0bi3Z

    Shin0bi3Z New commenter

    Keeping it simple that is good.
    CHuynh likes this.
  10. Shin0bi3Z

    Shin0bi3Z New commenter

    Do you start on the right side first or the left side first?
  11. Shin0bi3Z

    Shin0bi3Z New commenter

    I like it, another way of doing it in your head.
  12. BG54

    BG54 Occasional commenter

    Units first, then tens.
  13. yodaami2

    yodaami2 Lead commenter

    Yup, that's how I did it.
  14. maths_mikey

    maths_mikey New commenter

    Why do three sums when you can do 2? 27+8 =35 35+40=75
    Shin0bi3Z likes this.
  15. Shin0bi3Z

    Shin0bi3Z New commenter

    OK got you.
  16. Shin0bi3Z

    Shin0bi3Z New commenter

  17. briceanus

    briceanus New commenter

    Sorry, but this is inefficient and open to error.
    round up, round up, add tens, add units, subtract.

    20 +40 = add
    7 + 8 = add
    60 + 15 = add
    addition is simpler than subtraction, 3 operations is quicker than 5. IMO
    Shin0bi3Z likes this.
  18. Shin0bi3Z

    Shin0bi3Z New commenter

    That is a great point, something to think about.
  19. Shin0bi3Z

    Shin0bi3Z New commenter

    You prefer efficiency in doing math, well done
  20. Bensusan

    Bensusan New commenter

    Left to right.
    Shin0bi3Z likes this.

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