Focus on Math

Helping children become mathematicians!

Number Sense: Anchoring to 100 October 17, 2013

Filed under: General Math,Parents,Primary Math Ideas & Problems — Focus on Math @ 9:13 pm
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Screen shot 2013-10-17 at 9.08.13 PMI was working with a teacher today, and in the course of our conversation we were talking about the relationship of numbers to  “anchor” numbers. For low numbers we anchor to 5 and 10. For larger numbers we anchor to multiples of those.

I have previously written about anchoring to 20, anchoring to 30, and anchoring to 100.

I wanted to add here a great activity sheet that anchors numbers to 100. The student colors the particular number (given by you or generated by dropping a bean on a 100 chart, etc.) and then looks to see how many more it takes to make 100.

The activity makes a great number sense warm-up activity for young students.

Thanks, Pat, for commenting about the colouring. I have students use the broad side of a highlighter for this task (or a wide light-coloured marker would also do nicely. We always swipe across a full row at a time (or at least in fives). I particularly stress that they are NOT to colour one dot at a time, that the important thing is to represent the number. It’s NOT art class here 🙂

I prefer using the 100 dot-array to a solid 100 grip because of the vertical and horizontal “anchoring” lines. It is easy, for instance to colour 60 and not lose track, colouring too few or too many rows: one colours the first 5 rows (to the anchor line) and one more row.

Download the anchoring to 100 activity sheet here.

Mathematically yours,


filled in how far to 100


2 Responses to “Number Sense: Anchoring to 100”

  1. Pat Lore Says:

    Nice idea! My only suggestion would be to use a grid instead of the hundred dots. Seems to me there might be a lot of time spent colouring in each dot – a grid would probably mean less time colouring, more time thinking.

    • Ah, so true, Pat. I guess I should have explicitly mentioned (and I will go back and add it in the body of the text) that I have students use highlighters to colour and ALWAYS have them swipe across a full row at a time! The girls, especially, want to colour each dot, but I stress that it is not art class! We are representing the number. Thanks for the response.

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