## 22 February 2015

### 5 Maths Gems #25

Back in Gems 18 I featured five ideas from the first 100 issues of Chris Smith's newsletters. I promised I'd be back with more newsletter gems, so today's post features some highlights from issues 101 - 250.

Chris's newsletters are very popular amongst maths teachers - he now has over 1,000 subscribers. Each week's newsletter is full of teaching ideas, puzzles, jokes and mathematical trivia - it's always a pleasure to read. If you don't already subscribe, email Chris to get on the list.

1. Number Stories
In Issue 123, Chris featured an idea for developing mathematical vocabulary. Students create their own number stories - this can be as simple or complex as you like. Chris included the basic example below for inspiration.
2. Fractions and Percentages
Another simple but effective activity was featured in Issue 113. Students pair off the numbers below (which you could print onto cards) to form fractions equivalent to the percentages in the table. One answer is already given.
3. Remembering Bearings
There's three key points that students need to remember about bearings. And remembering them is as easy as 123...
This idea originated from @kimmychuck and featured in Newsletter 245.

4. Guess Who
In my post about Desmos Polygraph I described it as a digital (and mathematical) version of Guess Who. Back in Issue 210, Chris wrote about a similar idea (originating from Jennifer Clark) which uses actual Guess Who boards - these are available for £3.50 on eBay. The picture below shows a guessing game for famous mathematicians. Jennifer also suggests putting the numbers 1 - 24 in the holders. For example I might choose the number 12 and my partner would have to ask me questions (eg is it prime?, is it a multiple of 4? is it square? etc) to work out what number I've chosen by a process of elimination. This is a nice way to develop vocabulary and knowledge of number properties. It could be used for other topics eg polygons, linear graphs and parabolas. I'm not sure it would be practical to set this up for a whole class, but it would be a nice activity for keen parents to do at home with their children if they have an old Guess Who game.
5. Factor Visualisation
These animated factorisation diagrams are lovely. They're worth showing to your students when you teach prime factorisation. The animation moves quickly but can be paused and reversed. It shows numbers arranged in accordance with their prime factors. For example, 9 is shown as three groups of three, 10 is five groups of two and 11 is prime, so there is no grouping.
 Visualisations of 9, 10 and 11
The animation is mesmorising.  Background information is available here.
 189 = 7 x 3 x 3 x 3
Extras
Chris includes a puzzle in every issue - they're pretty challenging and great fun for maths teachers. The puzzle below is one of the easier ones - I think this would be accessible to all students and suitable for any age group.