Q&A #16325

Rounding Decimals

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From: Gail (for Teacher2Teacher Service)
Date: Nov 29, 2005 at 23:18:37
Subject: Re: Rounding Decimals

You might consider using money as a model for this activity.  Ask students
about how many dimes they have (rounding to the nearest tenth) or about how
many pennies they have (rounding to the nearest hundredth).

I find that when I pair my rounding instruction with number lines and
thoughts about "halfway", it helps students, too.  In this case, making
sure they understand that halfway between two "ones", like 36 and 37, is
36.5, so any amounts between 36 and 37, but less than that halfway point,
will be rounded to 36, and any amounts greater than 36.5, but less than 37,
will round to 37.

Extending that to tenths and hundredths, you might think about what is
halfway between 0.6 and 0.7, namely, 0.65, and what is halfway between 0.06
and 0.07, namely 0.065.  This will require students to recognize that 0.6 =
0.60 = 0.600, etc.

The more you can tie what students are exploring into concrete examples, the
better able your students will be to form mental images that will help them
generalize the "rules" they are discovering.

Hope this helps,

 -Gail, for the T2T service

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