跟讀練習: Math Antics - What Are Percentages? - 通過影片學習英語口語
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Hi! Welcome to Math Antics.
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Now that you know all about fractions, from watching all of our fractions videos, it’s time to learn about something called “percentages”.
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Percentages are super important.
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Have you ever been in a math class and heard another student ask the teacher: Um.. excuse me… teacher… Ah… when are we ever gonna use this stuff?
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Ya know… like in real life?
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Well when it comes to percentages, the answer is one-hundred percent of the time.
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Well alright… maybe not a hundred percent of the time… but a lot!
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Percentages are used every day to calculate things like: …how much sales tax you pay when you buy something.
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…how much something costs when it’s on sale.
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…how much fiber is in your granola bar.
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…or how much money you can make if you invest it in the stock market.
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That’s all real life stuff for sure.
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So, you can see that it’s really important to understand percentages and how we use them in math.
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Alright then… are you ready to learn the key to understanding percentages, or percents as they’re called for short?
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Drum roll please… A percent is a fraction!
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Whaaaat? That’s right… a percent IS a fraction!
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And since you already know all about fractions, learning about percents is gonna be easy.
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But a percent isn’t just any old fraction. A percent is a special fraction that always has 100 as the bottom number.
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If it’s a percent, then no matter what the top number is, the bottom number will be 100.
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In fact, because the bottom number of a percent is always 100, we don’t even write it.
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Instead, we use this handy little symbol (%) called a percent sign.
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Whenever you see this symbol after a number, it means the number is a percent.
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It’s really a fraction with 100 on the bottom, but it’s just being written in this more compact form.
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...like this number 15 here.
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It’s got the percent sign after it, so we read it as "15 percent", and because a percent is really a fraction that always has 100 as the bottom number, we know that it means the same thing as 15 over 100.
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Percents make even more sense if you know what the word precent means.
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The prefix of the word (per) means “for each” or “for every”. Ya know like if someone said, “only one cookie per person”.
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And the root word (cent) is Latin for 100. That’s why there’s 100 cents in a dollar.
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So, percent literally means “per 100” and that’s why they’re shortcuts for writing fractions that have 100 as the bottom number.
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Alright then, so whenever you see a percent like this, you know it can be replaced with (or converted) to a fraction.
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Let’s look at a few examples so you see the pattern.
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3% means 3 over 100 10% means 10 over 100 25% means 25 over 100 and 75% means 75 over 100 These are percents… and these are the fractions that they stand for.
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There’s a few other interesting percents that we should take a look at.
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…like this one: 0% …can you have 0% ?
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Yes! 0% would just mean 0 over 100. It’s what we like to call a “zero fraction” cuz its value is just zero.
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Remember, it’s okay to have zero on the top of a fraction, but not the bottom!
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Alright then, what about 100%. Well 100% just means 100 over 100. That’s what we like to call a “whole fraction”.
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The top number is the same as the bottom, so its value is just one whole, or 1.
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Okay then, 0% is just zero, and 100% is just 1.
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But what about numbers bigger than 100? Can you have 126% ?
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Yep, it works exactly the same way. 126% just means 126 over 100.
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And you know from the fractions videos, that’s what we call an “improper fraction”.
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The top number is bigger than the bottom number, so the fraction’s value will be greater than 1.
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Alright team, I want you to go out there and give me a-hundred and TEN percent effort in today's game!
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But coach… it would be “improper” for us to give a-hundred and ten percent effort in today’s game.
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Okay, so now you know the key to percentages. …that they’re just special fractions that always have 100 as the bottom number.
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But there’s one more thing that I need to tell you about in this video, and that’s decimals.
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Do you remember in the video about fractions and decimals that you can convert any fraction into its decimal value?
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Sometimes it was kind of tricky converting to a decimal if we had to divide the top number by the bottom number.
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But other times, like when we had “base-10” fractions, it was easy because decimal number places are made for counting base-10 fractions, (like tenths, hundredths and thousandths).
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Well guess what… Percents ARE base-10 fractions! They are hundredths because their bottom number is always 100.
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That means it’s really easy to re-write a percentage as a decimal number.
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You can do it the same way as we did in the base-10 fractions video.
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For example, we know that 15% is just 15 over 100, right? That’s its fraction form.
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But it also has the decimal form 0.15 because THIS is the hundredths place and 0.15 means 15 hundredths.
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So, we can re-write 15% as a fraction (15 over 100) OR as a decimal (0.15) And now that you know WHY we can easily convert a percentage to a decimal, let me show you a really simple trick for doing it.
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First, you start with the number in percent form like this: 35% Next, you imagine where the decimal point should be in the number 35.
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It’s not shown, but if it was, it would be right here next to the ones place.
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(Now remember, 35 and 35.0 are the same value.) Now that you know where the decimal point is, just move it two number places to the left (away from the percent symbol) and draw it in right there.
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Last of all, once you have moved the decimal point, you erase the percent sign because you don’t have a percent anymore.
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Moving the decimal point two places to the left converted it into the decimal value of that percent.
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Let’s try converting a few more percents into their decimal values so you can get the hang of it.
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For 62 percent, we move the decimal point two places to the left and get 0.62 (Remember, we can put an extra zero in front of the decimal point to be a place holder and to make the decimal point easier to notice.) For 75 percent, we move the decimal point and get 0.75 For 99 percent, we move the decimal point to get 0.99 Pretty Cool, huh?
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Okay, but what about 4% ? You might wonder how we can move the decimal point two places over when our number only has one digit.
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But all we need to do is use a zero as a place holder in the number place that’s missing.
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Then, when we move the decimal point two places over, we end up with the decimal value of 0.04.
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Now that makes sense because 4 is in the hundredths place and 4% is 4 over 100.
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And in the same way, 1% would just be 0.01. Again, we need that extra zero placeholder.
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Here’s a few more interesting examples: 0% would be just 0.00 And if we have 100% and we move the decimal point two places to the left, we end up with 1.00 But 1.00 is the same value as 1. That’s why 100% represent one whole.
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And if we have 142%, we move the decimal point to get 1.42 That’s a value greater than one which is what we’d expect because 142% is really an improper fraction (142 over 100) Its value should be greater than 1.
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Alright, so now you know that a percent is a special fraction that always has 100 as the bottom number.
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And you know that you can re-write percents in either their fraction form OR their decimal form.
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25% is 25 over 100 or 0.25 But keep in mind that you could go the other way too.
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If someone gives you a fraction with 100 as the bottom number, you can re-write it in percent form.
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If you get 12 over 100, you can say that’s 12% And if you get 80 over 100, you can say that’s 80% OR… If you get the decimal 0.10, you can say that’s 10% and if you get the decimal 0.38, you can say that’s 38% So, that’s the key to percentages. They’re another way to write fractions and decimals.
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But there’s a lot more to learn about how they‘re used in math, and we’ll learn more about that in the next few videos.
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But for now, you should be sure that you really understand the basics of percentages by doing the exercises for this section.
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Thanks for watching Math Antics, and I’ll see ya next time!
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Learn more at www.mathantics.com
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關於本節課
在本節課中，您將學習關於百分比的重要知識。百分比與分數之間的關係將幫助您更輕鬆地理解數學中的各種概念。您將瞭解到百分比是如何在日常生活中使用的，比如購買商品的銷售稅，瞭解食品中的營養成分，或者投資於股市能獲得多少收益。通過了解和練習，您能夠在生活中自信地應用這些知識，同時提升您的英語口語能力。
關鍵詞彙與短語
- 百分比 (percent): 表示每一百中有多少的量。
- 分數 (fraction): 一種數學表達方式，表示部分與整體的關係。
- 銷售稅 (sales tax): 購買商品時需要支付的額外費用。
- 投資 (investment): 將資金投入某個專案或市場以獲得收益的行為。
- 零分數 (zero fraction): 分子為零的分數。
- 完整分數 (whole fraction): 分子與分母相等的分數。
- 不規則分數 (improper fraction): 分子大於分母的分數。
- 每個 (per): 表示分配或比例的用法，與“百分比”緊密相關。
練習建議
在進行口語練習時，您可以使用 shadow speak 的方法來增強您的發音和流利度。首先，觀看這段關於百分比的 看YouTube學英語 影片，並嘗試在每次觀看時跟著說。影片中的語速適中，發音清晰，非常適合進行 shadowing 練習。儘量模仿影片中講者的語調和情感，使練習更具真實感。
同時，在練習時，可以使用 shadowspeak 技巧，即在重複句子時嘗試新增自己的例子，例如自己購物時所付的稅率或投資的想法。這種結合真實生活的練習能幫助您更牢固地掌握內容，提升對英語的理解和應用能力。通過不斷反覆，您會發現在表達與碰到百分比相關的問題時，將變得更加自信與自然。
影片中的語法
說話人最常用的結構，並附上影片中的原話：
| 結構 | 影片中的用法 |
|---|---|
| 被動語態 be + 過去分詞 — 強調發生了什麼，而不是誰做的 | being written · can be replaced · are made |
| 現在完成時 have/has + 過去分詞 — 過去發生但與現在仍有關聯的事 | Have you ever been · have moved |
| 用 “should” 提建議 should + 動詞 — 表示應該做的事 | should take · should be |
| 比較級 -er than / more … than — 比較兩個事物 | bigger than · greater than |
什麼是跟讀法？
跟讀法 (Shadowing) 是一種有科學依據的語言學習技巧，最初開發用於專業口譯員的培訓，並由多語言者Alexander Arguelles博士普及。這個方法簡單而強大：您在聽英語母語原聲的同時立即大聲重複——就像是一個延遲1-2秒緊跟說話者的影子。與被動聽力或語法練習不同，跟讀法強迫您的大腦和口腔肌肉同時處理並模模擬實的講話模式。研究表明它能顯著提高發音準確性，語調，節奏，連讀，聽力理解和口語流利度——使其成為雅思口語備考和真實英語交流最有效的方法之一。