These questions test a lot of things so use them carefully.
Firstly there is what do we understand about reciprocals, namely:
These are tricky concepts to grasp. This is the order in which I teach them, but I don’t think the “flow” through these 4 concepts is particularly obvious and students need to be carefully led with lots of examples using Mini Whiteboards.
Other understanding required includes:
- Finding equivalent fractions
- Finding common denominators and using them to find the right equivalent fractions
- Adding fractions
- Converting between Mixed Number and Top-Heavy fractions
- Negative fractions
And the last question took me a good 3-4 minutes to convince myself I had the right answer. Which always makes me stop to think – am I being fair to my students here?
So, at #MathsMeetGlyn last weekend Don Steward briefly put this picture up on the screen but then decided to talk about something else as time was pressing.
That’s a bit like a “Wet Paint” sign. You have to touch it just to see if it really is wet…
So I had a little play with these. I couldn’t find anything about it on his blog but of course there is lots of other lovely stuff there.
A few different questions you could pose here:
- What is the ratio of red area to blue area?
- What is the red area as a fraction of the blue area?
- What is the red area as a fraction of the whole circle?
- What is the blue area as a fraction of the whole circle?
And then of course, can we generalise? What about when there are n small circles. What happens as n gets bigger? Why? Can we find a general expression for the area?
Have a go. It actually turns out to be quite simple but depending on which question you start with, you can get into a lot of practice with ratio and dividing fractions.