Keeping with the theme from Ioan’s ‘Magic Maths‘, Finny set up some Harry Potter challenges for Ioan. Again, they were looking at place value.

What is place value?

Place value is the value of each digit in a number. It is important that children understand that while a digit can be the same, its value depends on where it is in the number. 

For example, the 5 in 350 represents 5 tens, or 50; however, the 5 in 5,006 represents 5 thousands, or 5,000


  • Harry Potter Lego
  • Jelly in measuring jug
  • Worms cut to various lengths
  • Number lines
  • Measuring scales filled with insects
  • Place Value Disks
  • Whiteboards and pens

Problem solving

Finny explained that Ioan had to collect the Harry Potter characters as he worked through the activities and take them to the final challenge.

Ron needs slime for a potion. How much slime does he have?

This involved reading the scale on a jug. Having looked at examples of reading figures on number lines, it’s always useful to represent the number line in ‘real life’ ways.

What is a Number Line?

The most simple number lines will essentially be a horizontal line with numbers evenly spaced from each other along the line, with a specified starting and ending point. Numbers get larger as you move right and smaller as you move left along the line. The number line can go on left and right forever.

Can you use the number lines to work out the length of the worms?

The first number line went from zero to one hundred, so Ioan worked out the intervals between the two numbers.

Intervals are all the numbers between two given numbers. In this case 0 and 100, so the midpoint would be 50, a quarter of the way along would be 25 and three quarters of the way would be 75.

There were no length units on the number line so Ioan decided they would be centimetres. This made the worm 75cm.

The second number line ran from zero to one hundred thousand. Ioan followed the same process to work out the midpoint and other intervals.

The third number line went from zero to one thousand.

The fourth went up to ten thousand.

Our memory card was full so we had to stop filming part way through the fourth number line, here is the rest of the example.

Ioan paused to compare the varying lengths of the worms. He pointed out that the shortest worm (on the plate) was actually the longest when using the number line, being 25,000cm. Whereas the one which looked like the longest worm (on the plate) was only 1,000cm.

In the fifth example, the number line was shown with the same four intervals as in the previous examples. Ioan recognised that he would need additional intervals to work out the answer.

The final example was particularly tricky as the number line started from 1,000 and again couldn’t use the main four intervals.

How much do the insects weigh?

Another variation on reading scales.

Which month did Hermione read the most books?

For this one, Ioan had to recognise the place value of each digit in the five-digit number (ten thousands, thousands, hundreds, tens, and ones) and compare them.

The Hogwarts Express is ready to go. Please can you put it on the right platform?

They sat back to look at the challenges Ioan had completed.

They then went on to work out how to evenly split the worms between them.

That’s the end of our place value work and it’s safe to say that we have LOVED doing our first unit of Maths home education, ‘Curley style’.

DfES National Curriculum (2013)

Numeracy Year 4 programme of study

Number – number and place value

  • count in multiples of 1000
  • find 1000 more or less than a given number
  • recognise the place value of each digit in a four-digit number (thousands, hundreds, tens, and ones)
  • order and compare numbers beyond 1000
  • identify and represent numbers using different representations
  • solve number and practical problems that involve all of the above and with increasingly large positive numbers