# Common Core Math Facebook Rant

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So my friend on FB just posted that her 4th grade son encountered this problem:

\$78.40 divided by \$2,234.46

Um, OK. At first I'm scratching my head and worrying because my 4th grader (CLE Math) is nothing near doing anything like this. Then I realize that I took college calculus and pharmacy math and I calculated dosages of live or die medications for 2 pound premature babies for a living and never encountered anything like this. Should I (we) be worried?

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I'd wonder (1) whether there's a lot of context missing, e.g., it's really some sort of estimation problem, and/or (2) whether there's a typo, e.g. the bigger number was intended to be the dividend.

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I'd wonder if perhaps your friend doesn't understand the difference between divided "by" and "into".

I'd also wonder if calculators were allowed.

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What they said. There's no reason you can't perform the calculation, but it's not a reasonable calculation to do by hand.

If you do 2234.40/78.40, you get 28.5 exactly. It seems that it's been swapped somehow and probably an estimation problem.

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The dollar signs are making me wonder.  The idea of "dollars divided by dollars gives a unit-less answer" is pretty advanced for fourth grade.
Like previous posters, I'm guessing typo, mistranslation, and/or more context needed.

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Well, I could see a problem such as "Jenny sold some stuff at \$78.40 per kilo, and she made \$2234.40, how many kilos did she sell?" or something like that. (although that would be some expensive stuff! better be made of gold or something!)

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Worried about what? That you're behind where the schools are?

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Well, I could see a problem such as "Jenny sold some stuff at \$78.40 per kilo, and she made \$2234.40, how many kilos did she sell?" or something like that. (although that would be some expensive stuff! better be made of gold or something!)

Yeah, but to match the problem given it would have to be \$2234.40 per kilo making \$78.40 total, how many kilos did she sell, with the answer being a fraction of a kilo.  (And yea, that would be expensive stuff!!!)  And even then, the units would be kilos, whereas the original problem had a unit-less answer.

It's a tough one to provide a context for, that's for sure!

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Yeah, but to match the problem given it would have to be \$2234.40 per kilo making \$78.40 total, how many kilos did she sell, with the answer being a fraction of a kilo.  (And yea, that would be expensive stuff!!!)  And even then, the units would be kilos, whereas the original problem had a unit-less answer.

It's a tough one to provide a context for, that's for sure!

Oh yeah, that's why I thought whoever shared it had gotten what was supposed to be divided into what reversed.

Where was the unit-less answer? I didn't see that? Or did you also see it on fb?

I was guessing that whoever shared it just didn't realize there were more units involved.

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Discount? As in \$2,234.46 is original price and \$78.40 is sale price.

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Discount? As in \$2,234.46 is original price and \$78.40 is sale price.

Hmmm.  That would be (\$2,234.46 - \$78.40)/\$2,234.46, and you'd usually multiply by 100 to get the percent.  But if \$78.40 was the amount off, and you wanted the fraction of the discount rather than the percent, then that would work.  Of course, that's beyond what you'd normally give a fourth grader!

(And the answer is a non-terminating, non-repeating fraction, which is also a bit much for fourth grade.  Although with many students using calculators these days....<insert anti-calculator rant here>)

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(And the answer is a non-terminating, non-repeating fraction, which is also a bit much for fourth grade.  Although with many students using calculators these days....<insert anti-calculator rant here>)

not really -- it's a rational number, which means it MUST terminate or repeat -- it's just that the period is 42 (although as far as practicality goes I agree with you 100%)

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It is probabably either an error or a misinterpretation or both. The number of mistakes I find on a one page homework sheet is astounding. This week apparently 5+6=10.

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It is probabably either an error or a misinterpretation or both. The number of mistakes I find on a one page homework sheet is astounding. This week apparently 5+6=10.

It does.....in base11.

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My guess is it's an estimation thing.

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I would say it's an estimation thing -
2200/100 = 22

My 4th graders only do long division with 1 digit divisors. However, they learn to estimate and divide by multiples of 10 before tackling the long division. There's a lot left out of the problem that she posted (which seems to always be the case when parents post about CC problems).

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So my friend on FB just posted that her 4th grade son encountered this problem:

\$78.40 divided by \$2,234.46

Um, OK. At first I'm scratching my head and worrying because my 4th grader (CLE Math) is nothing near doing anything like this. Then I realize that I took college calculus and pharmacy math and I calculated dosages of live or die medications for 2 pound premature babies for a living and never encountered anything like this. Should I (we) be worried?

Don't worry. It's NOT a 4th grade CC standard.

Here is the 4th grade division standard from the CC standards website.  The highlighted is why I believe this to be an estimation problem. If the school follows closely to CC, then that division problem will not be feasible based on what they've learned previously.

CCSS.MATH.CONTENT.4.NBT.B.6

Find whole-number quotients and remainders with up to four-digit dividends and one-digit divisors, using strategies based on place value, the properties of operations, and/or the relationship between multiplication and division. Illustrate and explain the calculation by using equations, rectangular arrays, and/or area models.

Now, here is the estimation standard:

CCSS.MATH.CONTENT.4.NBT.A.1

Recognize that in a multi-digit whole number, a digit in one place represents ten times what it represents in the place to its right. For example, recognize that 700 Ã· 70 = 10 by applying concepts of place value and division.

The estimation standard easily applies to the problem, like I stated in my first comment. They can estimate the dividend to be 2200 and the divisor to be 100. That is well within the bounds of estimating and dividing by 10s, 100s, 1000s, which we do before long division.

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