Message-ID: <1972593744.9421.1563655220526.JavaMail.confluence@www.terc.edu> Subject: Exported From Confluence MIME-Version: 1.0 Content-Type: multipart/related; boundary="----=_Part_9420_1609725610.1563655220525" ------=_Part_9420_1609725610.1563655220525 Content-Type: text/html; charset=UTF-8 Content-Transfer-Encoding: quoted-printable Content-Location: file:///C:/exported.html Revisiting Subtraction

# Revisiting Subtraction

Donna Curry

=E2=80=94(2009)The Math Practitioner. Vol. 15, #2.

### Summary

For years, many of us learned that subtraction meant =E2=80=95"take away= ". We learned certain =E2=80=95tricks to handle those gnarly word problems.= We learned to look for words such as "less", "left", "difference", or "dec= reased by", to decide whether we should subtract or not. And, we learned th= at when we subtract, we always take the smaller number from the larger numb= er. [Any of us who has overdrawn on our checkbook knows that the larger num= ber doesn't always go on top!] Our adult learners have learned many of the = same notions about subtraction. It's important, especially for those studen= ts who struggle with "basic math concepts", that they revisit what subtract= ion is really all about.

In many cases, subtraction can be considered a situation in which we "ta= ke away" something. If I had \$200 in my checking account and now have \$75 l= eft, we could use subtraction to find how much I "took away". But what gets= taken away when we compare two quantities? What gets "taken away" if the h= igh temperature was 32 degrees and it is now 22 degrees? What gets "taken a= way" when we talk about the difference in our ages =E2=80=93 I was born in = 1985 (I wish!) and you were born in 1979?

Nothing is "taken away" in those examples. When we look at our ages, we'= re comparing two quantities. So, subtraction also is used to show the diffe= rence between them. If students don't realize this, they may not think of s= uch a situation as a subtraction problem. Whether they count up from 1979 t= o 1985 or whether they subtract 1979 from 1985, they need to understand tha= t comparing two quantities can be solved using a subtraction strategy.

------=_Part_9420_1609725610.1563655220525--