Monthly Archives: March 2013

52. Special Offer 2

I think you’ll agree that this is a pretty good offer:


A total saving of £7.94.

How about this one?


I know these are meant to be mix and match offers, but the numbers are just funny.

(PS: I hope the discount algorithm on the till system doesn’t automatically apply the offer price if you buy two of the second toy.)

50. When will I ever use this …


A prescription says to take 2 pills every 4 hours, but don’t take more than 8 pills in 24hrs. There are 100 pills in a prescription.

If you start taking them on the 22nd March, when do you stop taking them? Assume you start taking them at midday and are in bed by 2230.

You can’t get a more real-life maths problem than that!

49. Trial by rice

Trial and improvement seems to be a bit of a marmite topic. You get it or you don’t! It’s a bit abstract, has scary algebra and those little numbers floating in the air – what are they about then?

Practical trial and improvement

Try doing T&I using a more practical/visual approach.

Jug or bowl
Rice or other dried pulse
A big spoon
A medium spoon
A small spoon
(In fact as many different sizes as you want)

Tell the group you want a precise amount of rice in the jug eg 246g.
They can only use the spoons provided. Each spoon must be full – no half measures.


1. Ask a pupil to estimate what they think 246g is, without looking at the scale.

2. Using the big spoon, pupils try to get as close as they can by adding/subtracting spoonfuls. When they cannot get any closer, change to the medium spoon.

3. Repeat the previous step with the medium spoon.

4. Repeat the previous step with the small spoon.

(If you have smaller spoons, just keep going)

The Maths Bit
Each step in the process is equivalent to a step in the process of T&I.

1. Initial estimate of the solution
2. Narrowing to the nearest 10
3. Narrowing to the nearest whole number
4. Narrowing to the nearest 0.1
(More spoons, more decimal places)

This activity isn’t designed to help with substitution, but it does get across the concept of why you do each stage. It is a good memory aid too. Now when I revisit T&I and get the usual blank looks of ‘Seriously Miss, we have never done this before’ I just mention the rice measuring lesson and a series of little lightbulbs go on.

48. Percentage book

I’ve found that copying examples and methods into a useable revision resource can be tricky for younger pupils or those with concentration issues. They don’t refer back to their notes because they are either incomplete, unreadable, unfindable in their book or just lost.

I saw instructions for making simple books from a single sheet of paper and wondered if it was worth a try.

Non calculator percentage book

Making the book
Fold a sheet of paper into eight as shown. The sample here is A4, but I used A3 in class.


Cut along the middle two quarters (blue line in the picture) and fold in half lengthways.


Fold this into an X shape.


Arrange into a book.


Clearly label the cover – you want your pupils to find this easily.

As we filled in each page, I explained why we did each process. Because their books were larger, the bottom of their pages had questions too.


We covered 50%, 25%, 10%, 5%, 30% and the last page was a challenge/extension task: 17.5%.

The back page was left blank so that they could stick the mini-books into their exercise books.



47. Light bulb moment

Here is a ridiculously simple classroom tip that was thought up by one of my pupils today.



The class were using past GCSE questions, compiled in a Word document, photocopied back to back and stapled.



After completing a table of values, the question said ‘Use the graph paper below…’, except the graph paper had ended up three sides of A4 away due to a crazy quirk of Testbase (GCSE exam question software) and Word. Cue much mumbling and enough paper shuffling to make me think a hamster was rearranging his bedding!



One pupil simply asked if she could take a picture of the table of values, so she wouldn’t have to keep flipping pages.


So simple … pure genius!


Within 5 minutes, the class were quietly doing very accurate cumulative frequency diagrams, without silly mistakes and rustling.