A story
The calendar square
Draft: written by an AI helper and not yet checked by a teacher.
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A child tore this month's page off the wall calendar. Mum said: draw a square around nine days, three across and three down, and add them up. Tell me only the total, and I will tell you the day in the middle.
A child tore this month off the calendar. Mum: draw a square of around days, add them up and tell me only the total , and I will name the middle day.
square , total , middle day .
The child drew a square with 9 in its top corner: 9, 10, 11, 16, 17, 18, 23, 24 and 25. The total was one hundred and fifty-three. Mum divided it by nine and said: seventeen. She was right.
The square: . Total . Mum: . Right.
and .
Here is why. Take the days that face each other across the middle: 9 and 25, 10 and 24, 11 and 23, 16 and 18. Each pair makes thirty-four, which is twice seventeen. Four pairs make one hundred and thirty-six, and the middle day itself adds seventeen more.
Why: days facing each other across the middle: , , , . Each pair is . And , .
; .
It works for every month and every square: the four pairs make eight times the middle day, and the middle day itself makes it nine times. Divide the total by nine and the middle day comes back.
Every month, every square: if the middle day is , then , so .
and .
Letters of words: 612 → 228 → 26.
How to read the signs
- for every
- nine times n
- divided by
- times