Trains of thought

I’m back to spending large amounts of time sitting on Sydney trains. Three trains of thought (haha!) arose recently.

Throughout the carriages are a number of posters advising of good behaviour on trains, usually in rhyming couplets. One which is not a direct rhyme is:

Cover your cough
or sneeze please

This is undoubtedly meant to be ‘Cover your (cough or sneeze) please’, but the line break means that it could be interpreted as ‘(Cover your cough) or (sneeze) please’ – that is, instructing us to sneeze.

One young woman was carrying a cloth bag with a cartoon drawing of an stereotypical Mexican playing a guitar and the word ‘CHIDO’. The Urban Dictionary tells me that that’s a Mexican Spanish word for ‘cool’, but it’s also very close to the Korean word 치다 (chi-da), which covers ‘hit, beat, play baseball, golf, tennis etc, play drum(s), piano, guitar etc’. I first thought that the infinitive verb was chi-do, but it’s chi-da. ‘-do’ is a suffix in Korean, but it’s only added to nouns and pronouns, not verbs.

Each carriage has a four-digit identification number, displayed in moderately large numerals inside and outside the carriage. Some years ago, I read in the then daily free commuter newspaper about a game some people had devised, the object of which is to make those digits, in the order they appear, total 10, using any standard mathematical operation. I sometimes do this. Some sums are very easy. Some are very boring or unsatisfying (multiplying, dividing, powering by 1 to get the original number, multiplying by 0 to get 0 or powering by zero to get 1). (The number I discussed last week, 2520, could be (2×5) x (2^0), but is more interesting as (-2×5) + 20.) Some numbers don’t have a solution, at least within my attention span on that particular day. The best solutions use four different signs, in which case the first needs to be a minus sign.

One evening, the two carriages I was in had the numbers 6559 and 9126. For the first one, I found -6 + 5×5 – 9 = 10. For the second, I found two equations ((9 – 1) x 2) – 6 and ((9-1) / 2) + 6. I think those two are directly related, but I can’t immediately figure out how. (Sometimes there are two solutions which are not directly related, other than both totalling 10.)


5 thoughts on “Trains of thought

  1. The kids and I use to play a similar math game in the car. In CA the license plates usually have one number, followed by three letters, followed by three numbers. For example: 6ABC123. The game was to use the last three numbers equal the first number using any maths functions. So, the sample could be played as 1×2=2×3=6
    There was a game with the letters, too. The three had to be used in order, but any number of additional letters could be added to make as many words in as short a time as possible.


  2. Number plates in Australia when we were growing up were three letters and three numbers. Our game was to make a three word sentence or phrase from the letters. For example, our cousin’s wife was named Kate, and she had a VW Beetle with the number plate KZR, which she called ‘Kate’s Zippy Racer’.


    • that is another wonderful car game.
      by the way, I think I finally realized the significance of ‘astraya’! Is is a mispronunciation of Australia?
      Sometimes I can be so dense


  3. Pingback: Adventures in Numberland | Never Pure and Rarely Simple

  4. Pingback: Trains of thought, revisited | Never Pure and Rarely Simple

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