How to verify the square’s calculation yourself
Take the date, write out all its digits, compute the four additional numbers, add their digits to the pool and sort everything into cells from one to nine. Zeros don’t count. Ask Viki to show the calculation step by step and compare — discrepancies usually arise only in the additional-number rules.
The steps
- Write out the birth date’s digits in a row. E.g. 14.03.1991 → 1, 4, 0, 3, 1, 9, 9, 1.
- First additional number: sum all digits. 1+4+0+3+1+9+9+1 = 28.
- Second: sum the first number’s digits. 2+8 = 10.
- Third: from the first, subtract twice the first digit of the birth day. Day 14, first digit 1, doubled 2. 28 − 2 = 26.
- Fourth: sum the third’s digits. 2+6 = 8.
- Join everything: the date’s digits plus the digits of 28, 10, 26, 8.
- Sort into cells: how many ones, twos and so on up to nines. Skip the zeros.
Where results diverge most
- Handling zeros in the date.
- What to do when the third number comes out negative or zero.
- Whether to reduce two-digit results to one digit or keep both digits.
These are methodological differences between schools, not errors. That’s why two calculators may give slightly different squares — and both be «correct» within their own method.
Comparing with Viki
Write: «show the calculation of my square step by step». She’ll lay out the intermediate numbers, and it becomes clear at which step you diverged — if you did.
Why verify at all
To know a method stands behind the answer, not a mood. Recount by hand once — after that you can trust the calculation and spend your attention on the reading.
Viki writes out the steps — recount by hand.