Matt Parker, the internet’s own number ninja, has tweeted the following maths nugget:

Type any number into a calculator and then divide it by 7, 11 and 13. Why do the first six decimal places always sum to 27? #mathspuzzle

— Matt Parker (@standupmaths) November 12, 2012

Of course, the other version he’s tweeted, seen below, is going to be much more retweeted around the internet. But hey ho.

≈¡ZOMG!≈ Multiply your birth month and date, then divide by 77 and 13. If the first six decimal places add to 27, it’s a ≤POWER∞BIRTHDAY≥!!!

— Matt Parker (@standupmaths) November 12, 2012

No spoilers in the comments please – keep your enjoyment of maths strictly to yourself.

suppose your number was 1001 (ie 7*11*13) then it is not true, is there some other requirement for the puzzle? further we could say that the puzzle will fail for any multiple of 1001. As for the second consider someone born in 7/2002.

For the second puzzle I think date refers to the day of the month. So, someone born on 7/8/2002 would multiple 7 and 8 together. I don’t think the year factors into the calculation although the trick would still work with year unless year*month*date is a multiple of 1001.

The two tricks could be fixed by saying the sum of those decimals is always 27 or 0.