Last Monday I began what I thought was going to be a quick math lesson to explain a statistic that popped up in class, "80% of Minnesota's 3.2 million registered voters are expected to vote." But wait a second...when I went to unpack all of the math involved this is what we ended up doing:
First, a review of big numbers and the base ten system. You have to know what a million is and what a tenth of a million is. Second, rounding. Obviously, there weren't exactly 3,200,000 registered voters in Minnesota. How do you create an appropriately precise number for your purpose? Third, decimals. Here we have three wholes and two tenths. Students are often used to seeing decimal points but don't really know what they mean for anything other than money. Even in money, their understanding is shaky -- very few can articulate "tenths" and "hundredths" at the beginning of fourth grade. Fifth, using a place value chart to turn "3 whole millions and two tenths of a million" into a standard number.
All of that was for 3.2! We moved on to 80%. First I explained that "per" meant "for every" or "for each" and "cent" was Latin for 100. Once students know that "percent" means "for every hundred" they begin to be able to see its connection to decimals and fractions. We used base 10 blocks to further illustrate what 80% meant and then I very quickly exposed them to the procedure for finding out what 80% of 3.2 million is.
Whew. All of that for 7 words of text. It certainly reminded me of how much is involved in being numerically literate.
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