3.15用十进制四舍五入来估计总和和差异
章节大纲
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Juan goes to the store and purchases two items. One costs $21.95 and the other costs $14.25. He wants to estimate his total before he gets to the register, but he isn't sure how to estimate the values. What is an estimate of Juan's total?
::胡安去商店购买两件物品,其中一件费用21.95美元,其他费用14.25美元,他想在到登记簿之前估计他的总数,但他不确定如何估计价值。胡安的总数是多少?In this concept, you will learn how to estimate sums and differences of decimals.
::在此概念中,您将学会如何估算小数点的总数和差异。Estimating Sums and Differences
::估计和差额To estimate means to find an answer that is close to but not exact. It is a reasonable answer to a problem.
::估计如何找到接近但并非准确的答案,这是解决问题的合理答案。A sum is the answer of an addition problem. A difference is the answer of a subtraction problem.
::总和是附加问题的答案。差数是减法问题的答案。The easiest way to estimate a sum or a difference of decimals is to round the decimal. If you round the decimal to the nearest whole number, you can complete the problem using mental math or at least simplify the problem so that finding an answer is easier.
::估计总和或小数点差的最简单方式是四舍五入小数点。如果将小数点舍入小数点到最接近的整数点,您可以通过心理数学或至少简化问题来解决问题,以便更容易找到答案。Let's look at an example.
::让我们举个例子。Estimate 15.7 + 4.9 = _____
::估计数15.7+4.9=____In this problem, you only want to estimate the sum. You can do that by rounding each decimal to the nearest whole number.
::在此问题上,您只想要估算总和。您可以通过四舍五入每个小数点到最近的整数来做到这一点。In 15.7, the place being rounded is the 5. Look at the 7 and round up.
::在15.7中,四舍五入的地方是五舍五舍五入的地方,看看七舍五入的地方,然后四舍五入。15.7 becomes 16
::15.7变成16In 4.9, the place being rounded is the 4. Look at the 9 and round up.
::在4.9中,四舍五入的地方是四舍五入的地方,看看九舍五入的地方,然后四舍五入。4.9 becomes 5
::4.9改为5Next, rewrite the problem.
::下一个,重写问题。16 + 5 = 21
The answer is that 15.7 + 4.9 is approximately 21.
::答案是,15.7+4.9约为21。You can also use rounding when estimating sums of larger numbers.
::在估算较大数字的数值时也可以使用四舍五入法。Let's look at another example.
::让我们再举一个例子。Estimate 350.12 + 120.78 = _____
::估计350.12+120.78=____Round each number to the nearest whole number to find a reasonable estimate.
::每一组数字到最近的整数,以找到合理的估计数。350.12 becomes 350
::350.12变成350120.78 becomes 121
::120.78变成121350 + 121 = 471
The answer is that 350.12 + 120.78 is approximately 471.
::答案是350.12+120.78大约为471。Now let's look at estimations with subtraction.
::现在让我们用减法来看待估算。You can work on these problems in the same way, by rounding.
::你可以以同样的方式,通过四舍五入来处理这些问题。Estimate 45.78 - 22.10 = _____
::估计数45.78 - 22.10=______45.78 rounds to 46
::45.78发至46发22.10 rounds to 22
::22.10发至22发46 - 22 = 24
The answer is that 45.78 - 22.10 is approximately 24.
::答案是45.78 - 22.10大约是24。Examples
::实例Example 1
::例1Earlier, you were given a problem about Juan who wants to estimate the total cost of his purchases.
::更早之前,你曾听说 Juan想估计他购买的总成本的问题。Estimate the sum of $21.95 and $14.25.
::估计数额为21.95美元和14.25美元。First, round each decimal to the nearest whole dollar.
::第一,每一小数点到最近的整美元。$21.95 becomes $22
::21.95美元变成22美元$14.25 becomes $14
::14.25美元变成14美元Next, add the rounded values.
::下加四舍五入值。$22 + $14 = $36
Then, write the approximate sum.
::然后写下大约的金额$36
The answer is that $21.95 + $14.25 is approximately $36.
::答案是21.95美元+14.25美元约为36美元。Example 2
::例2Estimate $588.80 - $310.11 = _____
::588.80美元估计数 - 310.11美元=____美元First, round each decimal to the nearest whole dollar.
::第一,每一小数点到最近的整美元。$588.80 becomes $589
::588.80美元变成589美元$310.11 becomes $310
::310.11美元变成310美元Next, subtract the rounded values.
::接下来,减去四舍五入值。$589 - $310 = $279
The answer is that $588.80 - $310.11 is approximately $279.
::答案是588.80美元 - 310.11美元约为279美元。Example 3
::例3Estimate 2.67 + 3.88 = _____
::估计数2.67+3.88=____First, round each decimal to the nearest whole number.
::第一,每一小数点到最近的整数的四舍五入。2.67 becomes 3
::2.67变成33.88 becomes 4
::3.88变成4Next, add the rounded values.
::下加四舍五入值。3 + 4 = 7
Then, write the approximate sum.
::然后写下大约的金额7
The answer is that 2.67 + 3.88 is approximately 7.
::答案是2.67+3.88约为7。Example 4
::例4Estimate 56.7 - 22.3 = _____
::估计数56.7 - 22.3 = __First, round each decimal to the nearest whole number.
::第一,每一小数点到最近的整数的四舍五入。56.7 becomes 57
::56.7变成5722.3 becomes 22
::22.3变成22Next, subtract the rounded values.
::接下来,减去四舍五入值。57 - 22 = 35
Then, write the approximate difference.
::那就写下大致的差数35
The answer is that 56.7 - 22.3 is approximately 35.
::答案是56.7-22.3约为35。Example 5
::例5Estimate $486.89 - $25.22 = _____
::486.89美元估计数 - 25.22美元=____美元First, round each decimal to the nearest whole dollar.
::第一,每一小数点到最近的整美元。$486.89 becomes $487
::486.89美元变成487美元$25.22 becomes $25
::25.22美元变成25美元Next, subtract the rounded values.
::接下来,减去四舍五入值。$487 - $25 = $462
Then, write the approximate difference.
::那就写下大致的差数$462
The answer is that $486.89 - $25.22 is approximately $462.
::答案是486.89美元 - 25.22美元约为462美元。Review
::回顾Estimate each sum or difference by rounding.
::通过四舍五入估计每一总和或差额。- 56.32 + 23.12 = _____
- 18.76 + 11.23 = _____
- 14.56 + 76.98 = _____
- 11.12 + 54.62 = _____
- 33.24 + 45.32 = _____
- 18.97 + 15.01 = _____
- 22.43 + 11.09 = _____
- 4.52 + 3.21 = _____
- 19.19 + 27.75 = _____
- 87.12 + 88.90 = _____
- 67.19 - 33.12 = _____
- 88.92 - 33.10 = _____
- 76.56 - 3.45 = _____
- 65.72 - 11.12 = _____
- 77.34 - 43.02 = _____
- 88.02 - 11.10 = _____
- 89.32 - 18.03 = _____
- 24.67 - 10.10 = _____
- 37.82 - 14.20 = _____
- 55.88 - 44.22 = _____
- 334.56 - 125.86 = _____
- 456.11 + 112.18 = _____
Review (Answers)
::回顾(答复)Click to see the answer key or go to the Table of Contents and click on the Answer Key under the 'Other Versions' option.
::单击可查看答题键, 或转到目录中, 单击“ 其他版本” 选项下的答题键 。Resources
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