I have found that estimating on a number line was a big
shift for my class. At first, they
looked like EXPERT estimators; I was ready to hug their third grade
teachers. But then problems kept
cropping up. Why were they suddenly
struggling? Everyone knew that 48,053
rounds to 50,000 and everyone knew 21,923 rounds to 20,000.
It was pretty clear that when I asked them to round 34,356 to the nearest hundred and suddenly they looked like deer in the headlights that place value was the issue. Oh, they all whizzed through chapter 1 and knew their word form and expanded form and lined up numbers in columns like pros. And we've practiced regrouping on a daily basis in our Every Day Counts routine. But they are still not able to put it all together to really conceptualize how numbers differ.
To fix this I designed two activities. The first was "Pin the Number on the Number line." I started out with a single sticky note with the number 35,421 on it. Then I created four number lines on sentence strips based on that number. Each number line represented a different place value:
It was pretty clear that when I asked them to round 34,356 to the nearest hundred and suddenly they looked like deer in the headlights that place value was the issue. Oh, they all whizzed through chapter 1 and knew their word form and expanded form and lined up numbers in columns like pros. And we've practiced regrouping on a daily basis in our Every Day Counts routine. But they are still not able to put it all together to really conceptualize how numbers differ.
To fix this I designed two activities. The first was "Pin the Number on the Number line." I started out with a single sticky note with the number 35,421 on it. Then I created four number lines on sentence strips based on that number. Each number line represented a different place value:
Ten thousands:
10,000 20,000 30,000 40,000 and so on.
Thousands:
30,000 31,000 32,000
33,000 34,000 35,000 36,000 and so on.
And so on for the hundreds and tens...notice that the
original number will fit on both of the number lines. All the number lines were designed to have a
space where the given number would fit into.
Next I wrote 7 more sticky notes that could all fit
somewhere on the tens number line, since of course that line would have the
most limited choice.
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Estimating on Number Lines
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