The ‘600’ Block Misconception

As you may know, my PhD research looked at the place value understandings of Year 3-6 students. In this blog I wanted to share with you an interesting discovery I made through my research.

I call it the "600 block misconception".

Basically students with this misconception look at the Base Ten thousands block and think it is worth 600 instead of 1000.

Initially I was shocked by this error for two reasons.

1.The students were in Year 3-6, so I thought by that stage in their schooling, most would be experienced enough to recognise the value of the block.

2. Six hundred, seemed such a random response!

Well it turns out this is a relatively common misunderstanding (approximately 24% of Year 3-6 students in my research displayed this thinking). I believe it stems from the fact Year 3-6 students are often simultaneously learning in Geometry lessons that a cube has 6 faces and is hollow. When you look at a thousands block, it is a cube and it has 100 units on each face... so it makes sense that students think 6 by 100 is 600 (particularly if you use plastic Base Ten blocks which are hollow). For this reason, I encourage every school I work with to use wooden Base Ten blocks as they are weighted- 1000 literally feels like the weight of 1000 ones blocks!

I guess you are wondering... how can we help overcome this issue?

Well, like many things, we want students to discover the value of the block for themselves!

I simply hold up the block and say: "Today you are going to investigate this block and prove to me without doubt its value". And off they go!

I allow them to use blu-tac, ones, tens and hundreds blocks to explore this idea. You can see us doing this in the following video​

It is through this exploration that their understanding develops.

It is not enough just to TELL them it is a 1000 block...they have to DISCOVER it is in order to truly believe it!

So next time you are introducing the thousands block watch out for this misconception...it is more common than you think!

Want to learn more about teaching place value?

Check out my 'Assessing Place Value in Years 3-6' mini course. Click here to find out more.