A little while ago one of my students told me an interesting fact: he claimed that four is the only number where the number of letters in its name is equal to the number itself. This then clearly sparked something in one of my other students as the following lesson she disputed this fact, and said she knew another: ‘positive seventeen’. This generated quite a debate, with the initial student (who was rather disgruntled) saying that a space is a character and therefore that was incorrect. Her immediate response was ‘You said letters not characters’ and then (after a bit of scribbling in her book) ‘How about positive sixteen then?’ Well that was it, the gauntlet was thrown down and off they went. The entire class joined in and with considerable creativity decided to think about entire phrases where it could be true. They decided the rules: all characters were to be counted, which included any spaces and punctuation such as question marks.
If you want your students to have a go at this task I would definitely recommend mentioning the LEN formula in Excel spreadsheets!
Here are some more examples to start them off (and a couple of my favourites).
|16||one plus fifteen|
|42||fifty minus the square root of sixty four|
|21||XVII plus VI minus II|
|42||what is the product of three and fourteen?|
|∞||the infinite sequence one plus two plus three plus four plus five …..|
Please do post any interesting ones that your students, or you, come up with to add to this list.
All the best,
Debbie Barton is a teacher, examiner and maths consultant with over 20 years’ experience. She’s written a number of books including Complete Mathematics for Cambridge Secondary 1. She also worked as a Gifted and Talented trainer and is passionate about ensuring able students are challenged with exciting stimulus.