Simplifying radicals? Who needs it?

There was a time I thought radicals should be simplified. A factor of a radicand should never be a perfect square. To do otherwise was just sloppy math—so I thought. Now, I think differently. You should consider it too.

image square roots
pic fromthemathlab.com

Making the square root of 40 look like 2 on the square root of 10 serves no real purpose in the mathematics of real life. You can readily estimate the square root of 45, but trying to do that with three square root 5 is a much more complicated task, and for what? If I am going to the fabric store and I am asked how much ribbon I want, I better not say, “4 root 2” and expect to get the correct amount. At the hardware store, I am far better reasoning that the square root of 32 feet would be a bit less than 6 feet, and a bit more than 5 and one-half feet and just say 2 yards. The lumber department does not want to hear this nonsense about radicals and square roots.  They want to cut my lumber and send me to the register to check out so they can help the next person also get a reasonable amount of lumber.

real square roots
Photograph by question_ev3rything on reddit

Now, I know, one needs to simplify radicals to combine radicals via addition, such as the square root of 27 plus the square root of 12, but seriously. This is not reality. This is a contrived problem that I have never seen come up in real life. Ever. And I sew and measure and do real life things with math—at home. It does not come up.  It’s clever, like a party trick, but not terribly useful.

I do make certain my Math 2 students can “simplify radials,” but just for the “man.” Not for real life. I used to “ding” my students (take off 1 point just to be mildly irritating to get them to conform to convention) for not simplifying radicals. I am totally rethinking that.

Reality says leave radicals as they are so they are easy to estimate to be useful and to check for reasonableness. Done.

Skirt and shirt made out of fabric that has root vegetables that are in the shapes of rectangular prisms.
Last spring’s project…square roots…get it?

 

One thought on “Simplifying radicals? Who needs it?

Add yours

  1. I really agree with not needing to reduce the radical, esp. when purchasing the sq root of 28 feet of border for the garden. But, there’s just something that says to me that we need to keep these skills up mentally to keep our mind going. It’s so hard to undo what I was taught back in the 80’s. Sometimes I think the kids aren’t challenged enough. I gave them a worksheet from an old HOLT wkst with word problems. Even back then, they weren’t really practical problems, but it made them think and apply the skill of using mathematics and thinking critically. The students even commented that the problems were harder than the ones they usually see (such as on our STAAR test).
    I understand that we need change, otherwise we’d still be riding horseback to work. (and that dinging for not simplifying the radical… should that hold true for not reducing the fraction?) Thanks for always making this Texan think a little more than normal!

    Liked by 1 person

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