From the Daily Mail:
Maths magic! Sum that tells anyone's age and shoe size in just six simple steps
It’s the arithmetical trick that’s been causing delight and surprise but you’d better try it out on friends soon – because the later it gets into the year, the less likely it is to work.
Currently doing the rounds on social media, the poser involves a series of simple questions.
First ask your friend to think of their shoe size, then – using a calculator or a pen and paper – they should multiply it by five.
Next they add 50, and then take that total and multiply it by 20. They should add 1,015, and finally subtract the year of their birth.
Magically, the result should be their shoe size and age, together making up a three or four-digit number. The trick works regardless of whether you use UK, European or American shoe measurements.Questions:
- Does it work?
- Why does it work?
- Can you think of a way to break it?
- Is there a way to fix any problems?
Later in the article:
However, it won’t work for someone who has already had their birthday this year, or who is more than 100 years old.You could add a step: "If you have had your birthday this year add 1."
You can probably tell if someone is older than 100...
The other problem is if someone has a shoe size that finishes with a half.
Source: http://www.dailymail.co.uk/news/article-3403186/Maths-magic-Sum-tells-s-age-shoe-size-just-six-simple-steps.html
