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(单词翻译:双击或拖选)
by Jason Marshall
In the last two articles we’ve talked about the meaning of multiplication1 and how to use this meaning to make multiplying fractions easier. Today, we’re going to put everything we’ve learned about multiplication to good use by learning how it can help us convert between different units of measurement. For example, how to convert from miles to meters, meters to kilometers, kilometers to light-years, and even more.
But first, the podcast edition of this article was sponsored by Go to Meeting. With this meeting service, you can hold your meetings over the Internet and give presentations, product demos and training sessions right from your PC. For a free, 45 day trial, visit GoToMeeting.com/podcast.
Why Do We Make Measurements?
Before we start talking about how to convert between various units of measurement, we should probably talk a bit about why we make measurements in the first place. The answer to “Why?” is pretty simple: We make measurements to quantify the world. It’s one thing to stand on the beach and note that the water occasionally crashes ashore2 as waves, but it’s an entirely3 different thing to note the height of the waves, how frequently they occur, how fast they are moving, and so on.
Making quantitative4 measurements (that is, measurements with numbers) allows us to understand why things happen—not just that they happen. And they even help us to predict what will happen next. Measurements are powerful! Of course, we make measurements for far simpler things too, like figuring out what size shoes or pants we wear, or whether or not the new sofa we just bought will fit through the front door (probably should’ve checked on that first). Quantitative measurements are a fact of life. So, how exactly do we make them?
What are Units of Measurement?
Well, that depends on what we’re measuring. If it’s length, we use something like a measuring tape. If it’s time, we use a clock. Or, if it’s weight, we use a scale. All of these measurement devices are calibrated5 to give quantitative measurements in some generally accepted “unit.” For example, a measuring tape could be calibrated to give lengths in inches, feet, meters, miles, or even light-years (though that would be a very long tape).
So, which of these distance units is the right one to use? Again, that depends on what we’re measuring. If it’s something relatively6 small like the size of a sheet of paper, then inches is probably the most appropriate since the answer will be a reasonable number of inches—perhaps 8.5” by 11”. If we used miles instead, the size of the same sheet of paper would be 0.00013 miles by 0.00017 miles—pretty awkward to work with! But if we’re measuring something much larger, like the distance from New York to Los Angeles, then miles or kilometers would be much more appropriate. The good news, however, is that besides issues of convenience, it doesn’t really matter what units you use to make a measurement because you can always convert from one system of units to another. How does that work?
What is the Multiplicative Identity?
Well, this is where math steps into the picture. In particular, a very simple idea in math called the “multiplicative identity.” The idea is so simple, in fact, that you might be apt to dismiss its importance. So what is this multiplicative identity? It’s the number 1. That’s it! But the really important part is called the “multiplicative identity property”: it says that multiplying any number by the multiplicative identity (that is, by the number 1) does not change the value of that number. In other words: 2 x 1 = 2; 1,000,000 x 1 = 1,000,000; and so on—the value of the number doesn’t change. After all, multiplying a number by 1 just means that we stretch it until it’s exactly the same size as it was initially—it means: “don’t do anything.” Yes, I know this is probably obvious. No, I don’t expect you to be surprised. But please don’t give up on our little multiplicative identity friend just yet, because its true power will soon be revealed.
How to Convert Between Different Units
But that big reveal isn’t going to happen just yet because I first want to give you a little time on your own to try and figure out how all this fits together. So, the question is: What is the method for converting from one measurement unit to another? And, in particular, can you figure out what the multiplicative identity has to do with any of this? Think about it, and then be sure to check out next week’s article to find out how it all works, how to do the actual unit conversions7 in different situations, and how to use some handy online tools to make the whole process even easier.
Wrap Up
Okay, that’s all the math we have time for today. Thanks again to our sponsor this week, Go to Meeting. Visit GoToMeeting.com/podcast and sign up for a free 45 day trial of their online conferencing service.
Please email your math questions and comments to..............You can get updates about the Math Dude podcast, the “Video Extra!” episodes on YouTube, and all my other musings about math, science, and life in general by following me on Twitter. And don’t forget to join our great community of social networking math fans by becoming a fan of the Math Dude on Facebook.
Until next time, this is Jason Marshall with The Math Dude’s Quick and Dirty Tips to Make Math Easier. Thanks for reading, math fans!
收听单词发音 |
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multiplication
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| n.增加，增多，倍增；增殖，繁殖；乘法 | |
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ashore
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| adv.在(向)岸上，上岸 | |
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entirely
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| ad.全部地，完整地；完全地，彻底地 | |
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quantitative
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| adj.数量的，定量的 | |
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calibrated
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| v.校准( calibrate的过去式和过去分词 )；使标准化；使合标准；测量（枪的）口径 | |
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relatively
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| adv.比较...地，相对地 | |
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conversions
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| 变换( conversion的名词复数 )； （宗教、信仰等）彻底改变； （尤指为居住而）改建的房屋； 橄榄球（触地得分后再把球射中球门的）附加得分 | |
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