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FOIL - It Doesn't Always Work!

In more advanced math classes, many instructors happen to hate "FOIL" (including me) because it only provides confusion for the students. Unfortunately, FOIL (fist, outer, inner and last) tends to be taught as THE way to multiply all polynomials, which is certainly not true. As soon as either one of the polynomials has more than a "first" and "last" term in its parentheses, the students are puzzled as well as off course if they attempt to use FOIL. If students want to use FOIL, they need to be forewarned: You can ONLY use it for the specific case of multiplying two binomials. You can NOT use it at ANY other time!

When multiplying larger polynomials, most students switch
to vertical multiplication, because it is much easier to use, but there is another way. It is called the clam method. (An instructor at the college where I teach says that each set of arcs reminds her of a clam. She’s even named the clam Clarence; so, at our college, this is the Clarence the Clam mehod.)

Let’s say we have the following problem:

(x + 2) (2x + 3x – 4)

Simply multiply each term in the second parenthesis by the first term in the first parenthesis. Then multiply each term in the second parenthesis by the second term in the first parenthesis.

I have my students draw arcs as they multiply. Notice below that the arcs are drawn so they connect to one another to designate that this is a continuous process. Begin with the first term and times each term in the second parenthesis by that first term until each term has been multiplied.
When they are ready to work with the second term, I have the students use a different color.  This time they multiply each term in the second parenthesis by the second term in the first while drawing an arc below each term just as they did before.  The different colors help to distinguish which terms have been multiplied, and they serve as a check point to make sure no term has been missed in the process.

As they multiply, I have my students write the answers horizontally, lining up the like terms and placing them one under the other as seen below. This makes it so much easier for them to add the like terms:

This "clam" method works every time a student multiplies polynomials, no matter how many terms are involved.

Let me restate what I said at the start of this post: "FOIL" only works for the special case of a two-term polynomial multiplied by another two-term polynomial. It does NOT apply to in ANY other case; therefore, students should not depend on FOIL for general multiplication. In addition, they should never assume it will "work" for every multiplication of polynomials or even for most multiplications. If math students only know FOIL, they have not learned all they need to know, and this will cause them great difficulties and heartaches as they move up in math.

Personally, I have observed too many students who are greatly hindered in mathematics by an over reliance on the FOIL method. Often their instructors have been guilty of never teaching or introducing any other method other than FOIL for multiplying polynomials. Take the time to show your students how to multiply polynomials properly, avoid FOIL, if possible, and consider Clarence the Clam as one of the methods to teach. 

A Go Figure Debut for a Buckeye Who's New!

The Caffeine Queen is my newest Go Figure Debut. We have a great deal in common, especially when it comes to THE Ohio State University…..Go Bucks! She has taught both regular education and special education. Like most effective teachers, she is always on the lookout for exciting new teaching strategies. She describes herself as a hands-on teacher who enjoys creating items that are kid friendly. 

She believes RESPECT should be a two way street in any classroom. She says her shining teacher moment occurs daily when she receives hugs from her students! She thinks a fun and welcoming classroom atmosphere, along with engaging and interesting lessons, is truly the recipe for success. The internet world has really brought her teaching to life, and she desires to share some of those ideas and insights with other teachers.

She currently has 54 products in her store, most priced under $4.00. Her store features many math resources for the elementary as well as for middle school. If you visit her blog, you can read interesting and motivating articles about how she teaches math. I particularly like her May 2nd article about multiplication and how she uses shapes to help those who are struggling with two digit problems that require regrouping. Even I can relate to her April 5th post about fractions because my college students still struggle with them!

Her featured free item is a one-page divisibility rules poster that can be used during math class when students are working on factoring, simplifying fractions, etc. A smaller version of the poster is included for students to use in their Interactive Student Notebooks (ISN) or binders so that it is always within reach. Finally, a short worksheet for individual students or partners is included so that they can work on the newly learned rules while committing them to memory.

Her highlighted paid resource is a graphic organizer designed to make teaching the standard multiplication algorithm of two digit multiplication a bit easier to understand. Several different versions of the organizer are included.

The first three ready-made worksheet pages are multiplication without regrouping, with answer keys included. (The standard algorithm is difficult enough for beginners to conquer without having to immediately worry about regrouping.) Once students are comfortable with multiplying without regrouping, they are ready to begin regrouping. Hopefully, regrouping will go more smoothly because of the time spent solving problems without regrouping, and since the students are now familiar with the process of two digit multiplication.

Right now take a few moments to investigate the Caffeine Queen’s store and blog. Once there, why not become a follower, or download something that is free, or better yet, pick up an educational resource for your classroom?