Why you can’t get correct change at the supermarket

Why you can’t get correct change at the supermarket

M.J. McDermott is a meteorologist in Seattle and a mom who’s on a mission to wipe out the fuzzy-thinking math curricula plaguing our schools and ensure that not only will the US someday once again be a leader in math and hard sciences, but we will also be able to find a retail clerk who can make change from a dollar without using the register.

If you’re over 30, are not in the educational establishment, and don’t have kids in school, you’re going to be astounded at what passes for math education today. Coddling and self-esteem as a primary concern is not limited to English and social studies.

Yet another reason we’re going to be homeschooling our kids, who will have a headstart on all those public school kids who can’t do math without a calculator. (I mean, seriously, fourth- and fifth-grade textbooks with 35-page chapters on how to use a calculator? Come on!)

Written by
Domenico Bettinelli
14 comments
  • I remember 10-15 years ago attending a school board meeting for a rural district. A fourth-grade teacher brought a few of her kids to the board meeting to show the board members what they had learned in math.

    The problem was dividing three brownies among five people evenly. One poor child suggested dividing each brownie into ninths to distribute. And this is a right answer. The school board members acted like this was wonderful.

    I leaned over to the person sitting next to me and asked, “Who gets to divide the crumbs?”

    So yea, this makes sense that they would do this?

  • I actually went searching youtube for viedos of cluster math last year when moms on a bulletin board I was reading got into a discussion about their children’s math classes. I couldn’t believe how complex schools had made something so simple.

    Yep. Reason #1,845,725 we will be homeschooling too.

  • The “new-fangled” methods do show the students how to reason, but MJ McDermott is right when she says that these alone do not suffice.  Students do need to learn the algorithms.

  • Wow.  Just wow.  We may be sending our kids to a Catholic school, and I can guarantee you now that I’ll be asking what math texts they use!

  • As a mathematician, I have actually used clustering to do complex calculations in my head.  One has to be clever about manipulating numbers to do this.  It is pointless to do it in the “straightforward” way illustrated in the film, and it is not always advantageous to do it even when one is clever with numbers.  For the vast majority of people, this sort of work would simply be a waste of time, and for mathematically clever people, it either comes naturally or is quickly generalized from seeing a single example.

    It seems to be the genius of modern educational methods that new and clever ways are constantly being devised for wasting the children’s time.  This trend was beginning to be evident even in the late 1960s.

    The effort to preserve children from the stresses and strains of ego-challenging subject matter and teaching techniques is a more modern innovation, one which I only became acquainted with when I took my first assignment as a priest in 2003.  In the early days, when “the new math” first hit the streets, the idea was to help children think logically about math.  Now the challenge is to get them to think about math at all, without taking any ego-reduction risks.

    The results were already well documented in the 90s.  American students had the highest self esteem and the poorest performance in the developed world when it came to so-called hard subjects.

    None of these innovations had the slightest impact upon the children of elites such as college professors, doctors, lawyers and politicians (and, perhaps I should also add,  statisticians working on human demographics).  All of them knew the score and insisted their children receive a real education.

  • I was in a small retail clothing store last year, when the computor portion of the cash register broke down. The clerk (about 19) and the manager (about 25) were completely at a loss. They got out pencil and paper and were turning themselves inside out trying to figure out what change was needed for a $13.73 charge from a 20 dollar bill. After watching the painful spectacle, I finally taught them how to count change. They looked at me like I had just multiplied the loaves and fishes. “Wow,” the manager said, “How did you ever figure out how to do that!” I was equally amazed. The clerk was a college student, the manager had a degree in business admin and not only could they not make change, neither one could do subtraction.
    M grandchildren have the textbooks shown in the video. It’s so sad. I do what I can.

  • This isn’t the first time math has gone haywire with silly experiments by academics. They sell new math texts and children go through life crippled by them.

    In the late 1960’s to mid 1970’s, I and many of my peers were afflicted with the New Math.  Tom Lerher did a song about this New Math, in which we had to do everything in base 8.  Which is like base 10, he explains, minus 2 fingers.

    http://www.youtube.com/watch?v=a81YvrV7Vv8

    Someone did this rather poor animation to the original song on you tube, although it does help visualize the rapid-fire lyrics. 

    BTW, Tom Lerher wrote and performed a lot of songs of satire and pure silliness. He graduated with a BA in math from Harvard at age 18, taught at a number of prestigious universities (although he never earned his PhD) and recorded a number of albums of satire and silly songs.  Poisoning Pigeons in the Park used to be played on Dr Demento regularly and it is one of my favorites. A number of his performances are on You Tube.

  • I remember seeing this a while back at Mark Shea’s site and passing it on to my mother, a high school algebra and trig teacher of thirty years.  Her comments were right on with those of Fr. Larry’s.

    Basically, we are getting too clever with teaching, and the kids are missing out a lot (as Terentia’s example shows…a skill I remember being drilled on in fourth or fifth grade).  As a child, I was already starting to see these type of “shortcuts”, and I remember thinking that a.) “this isn’t a particularly easy way to do things” and b.) “why bother”, since they didn’t explain why we would want to do estimates and the like.

    The fact is, as I got better at math (and I admit, I was a bit of a math nerd growing up), I started to understand how and why the classical algorithms worked, and from there, I developed my own shortcuts, many of which have the same basis as these shown here, even if they weren’t as formalized.  But without the fundamental understanding of mathematical operations, it’s like teaching someone how to change the oil on a car if all they’ve ever known is a horse-and-buggy.

  • I tutored some fifth graders in math a few years ago.  No wonder these poor kids were confused!  I wasted a lot of time trying to figure out these types of methods that the teacher and textbook were advocating.  I’m sure the kids’ parents were equally frustrated when the kids would ask for help with homework.  Why can’t we just solve the problems?

  • I watched the video with a sense of horror—the lattice method being the most confusing matrix going!

    I know that teaching concepts is more important than drill, but drill is so essential to functioning without calculators that to deny that skill to children is like eliminating reading because we have videos.  What do you do when the crutches aren’t available?

    I am a math phobic, but I figured out clustering on my own when confronted with estimating the results of multiplying large digit numbers by other large digit numbers.  Working with the round number thousands, then hundreds and adding them and doing the same with the tens gave an approximation of accuracy sufficient for many of my needs.  Now I’m at an age where I cannot hold those subtotals in my head to tally them, but when I could, it was great!

    As the earlier poster said, this is something to realize on one’s own—probably every one has their own method of clustering math data.

  • Like the lady in the video said about one of the new algorithms, it IS kind of fun…but only once you’ve mastered the regular way to do math!  Just like reading literature is only fun once you know how to read and have a developed vocabulary…otherwise it’s just frustrating.

    Drill and repetition is what kids are good at in the early years…later they learn how to be more abstract about things…I think the pushing of the “new math” methodology is another expression of encouraging kids to “question authority”—WHY is 21 x 36 = 806?  When the kids are older, you can reason with them…when they’re younger, sometimes the answer really IS just “because it is!”

    My brother was in a high school play (many years ago) and they sang the Tom Lehrer song mentioned above (“New Math”)…I’ve been looking for the lyrics to that for so long now, every time my kids would bring home some boneheaded math homework…we’re homeschooling now, too, btw.

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