After measuring the diameter (the straight line along the bottom of the rainbow) on Friday, we were ready to kick of this week by measuring the curved arches of the rainbows.


Some of our rainbows:

Measuring tools:

  • Ruler
  • Tape measure
  • String
  • Scissors
  • Paper and pencil


While Finn set out all of our rainbows to measure, Ioan pointed out that the biggest arch we own is the wobbel board. Finn was worried that the wobbel board was just an arch, whereas the rainbows were all semicircles. They agreed the carpet would work as the base of the rainbow. Next Finn was concerned that it was wooden, not rainbow coloured, but Ioan had a plan to fix that. He stuck magnatiles along the edge of the wobbel board to make a large scale rainbow. As soon as Finn realised what Ioan was doing, he joined in.

They ran out of blue and purple squares, but Finn wasn’t fazed, he just joined two triangles together to make a square.

Finn fetched his ruler to measure the red arch, but Ioan stopped him. He taught Finn how to use string to measure the arch:

They pulled the string taut across the wobbel board, then cut the string where the arch finished. They measured their cut length of string against the tape measure. They got 101 cm.

They then had the idea of checking their accuracy by measuring the arch with the tape measure. The rainbow didn’t entirely cover the wobbel board, so after some discussion they decided to measure to the bottom of the wobbel board. Afterwards they swapped places so that Ioan could double check Finn’s measurements. They both agreed it was 101 cm.

DfES Outcomes for EYFS and National Curriculum (2013)

Numeracy Year 1 programme of study

Number – measurements

  • compare, describe and solve practical problems for lengths and heights [for example, long/short, longer/shorter, tall/short, double/half]
  • measure and begin to record lengths and heights

Pupils move from using and comparing different types of quantities and measures using non-standard units, including discrete (for example, counting) measurement, to using manageable common standard units. In order to become familiar with standard measures, pupils begin to use measuring tools such as a ruler.