Area measures the space a 2-D (flat) shape takes up. We decided to measure and compare the space taken up in the semicircles of our rainbows.


  • Light box
  • Transparent magnetic counters
  • Magnetic wands
  • Grimm’s small rainbow

Some of our rainbows:


We started off measuring the area of the Grimm’s small rainbow. We used a light box and some transparent coloured counters to make it multi sensory.

We were lucky that Hen Taid (their great grandfather) was a radiologist, so we had his old light box. Alternatively, you can use a transparent storage box filled with Christmas lights.

Ioan and Finn had the idea of laying the rainbow arches on their side and using a Grimm’s building board to make some ‘grass’ below and complete their semi-cicle. They insisted on recreating their magnatile rainbow on the radiator behind them before starting.

Even though their rainbow arch was 3-D, they were measuring the area of the flat 2-D semi circle created by the shapes.

In the video above, I asked them to predict how many counters it would take to cover the base of each semicircle. For the blue semicircle, Ioan originally predicted 5, then swapped to 9 counters., Finn thought it would take 10 counters to cover the orange semicircle.

Once they had started laying their counters down, I gave them the option to revise their predictions. Ioan’s new prediction was 5 counters and Finn’s was 22 counters.

I then asked them to compare the area of the orange semi circle (20 counters) and blue semi circle (5 counters).

Finny knew that 20 was ‘five fours’ or (prompted) ‘four fives’. Ioan knew that made the area of the orange semicircle four times bigger than the blue semicircle.

The boys used the camera and took their own pictures of their rainbows with the light box switched on and off:

They carried on measuring the semi circles created with the other arches. Ioan had spotted that in the picture with the light box switched on, it was hard to read the numbers on the logs. He convinced Finn to swap the logs for magnetic numbers that were clearer to read in silhouette.

He told Finn, “I’m taking the letters off the green background because it is opaque and blocking out all the light, if I just leave the letters it will be easier to read. Do you remember the word for when something is see through?” Finn knew the word was transparent. Ioan also went on to explain, “If something lets some light through but you can’t see through it very clearly then it is kind of in between, so a bit opaque-y and a bit see through. That is called translucent.”

These were their measured areas, with the light box switched on and off:

We used our magnetic wands to tidy up the counters, they always find this part as fun as the playing itself. Finn told me that the magnetic wands would attract the counters. Ioan tidied up with speed, whereas Finn went for precision.

If you’re interested, I have written a post on rainbow maths activities for toddlers and we have done a toddler activity with the light box, magnatiles and magnets.

DfES Early Learning Goals (2017)

Understanding the world

ELG 15 – Technology:

Children recognise that a range of technology is used in places such as homes and schools. They select and use technology for particular purposes.

DfES Outcomes for EYFS and National Curriculum (2013)

Numeracy Year 1 programme of study


  • recognise and name common 2-D shapes

Numeracy Year 4 programme of study

Number – measurements

  • find the area of rectilinear shapes by counting squares

Science Year 1 programme of study

Everyday materials

  • become familiar with the names of materials and properties such as opaque/transparent

Science Year 3 programme of study


  • recognise that they need light in order to see things and that dark is the absence of light
  • recognise that shadows are formed when the light from a light source is blocked by an opaque object

Forces and magnets

  • observe how magnets attract or repel each other and attract some materials and not others