这部分需要会什么？
- 将百分数、小数和分数互换
- 识别百分比关系中的比较基准
- 根据部分量、整体量和比例中的两个求第三个
核心概念与公式
\(p\%=p/100\)。若 A 是 B 的 \(p\%\)，则 \(A=(p/100)B\)。B 是比较基准；要求 A 是 B 的百分之几，应计算 \(A/B\times100\%\)，前提是 \(B\ne0\)。
如果题目问“\(p\) 的值”且写作 \(p\%\)，最终通常填写百分数前的数，例如 25；如果问对应的小数比例，则为 0.25。应按题目的表达方式作答。
做题时怎样使用
- 圈出“谁的百分之几”，确定整体或比较对象
- 写出“部分量 = 比例 × 基准量”
- 求百分数时先求比值再乘 100，并检查答案的形式
容易混淆的地方
“A 是 B 的 120%”表示 \(A=1.2B\)；“A 比 B 多 120%”表示 \(A=2.2B\)。两句话不同。
用一个例题串起方法
知识点教学例题某班有 40 人，其中 14 人选择某门选修课。选择人数占全班的百分之几？
展开解题思路 ＋
以全班 40 人为基准，比例为 \(14/40=0.35\)，所以占 \(35\%\)。若题目要求 \(p\) 的值，则填写 35。
本知识点题库
先独立作答，再查看答案与解析。
百分比关系・求百分数挑战
A car dealership has only sedans, SUVs, and minivans for sale. On Monday, 20% of the vehicles for sale were sedans and 50% were SUVs. If there were 62 sedans for sale at the dealership on Monday, how many minivans were for sale?
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百分比关系・求百分数进阶
0.1197 is 0.09% of the number b. The number b is 25% of the number c . What is the value of c?
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百分比关系・求百分数进阶
Of 300,000 paper clips, 234,000 are size large. What percentage of the paper clips are size large?
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百分比关系・求百分数基础
Amara grows cherry tomatoes in her backyard. This year, she harvested 750 cherry tomatoes and gave 10% of them to her neighbor. How many of the harvested cherry tomatoes did Amara give to her neighbor?
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百分比关系・求百分数挑战
The weight of sample A is 468% of the weight of sample B, and the weight of sample A is 0.780% of the weight of sample C. If the weight of sample C is p% of the weight of sample B, what is the value of p?
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百分比关系・求百分数基础
Out of 300 seeds that were planted,80% sprouted.How many of these seeds sprouted?
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百分比关系・求百分数挑战
of 900,000 beads,828,000 are silver. What percentage of the beads are silver?
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百分比关系・求百分数进阶
For x > 0, the function f is defined as follows:
f(x) equals 201% of x
Which of the following could describe this function?
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百分比关系・求百分数进阶
13 is p% of 25.What is the value of p?
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百分比关系・求百分数基础
What is 10% of 470?
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百分比关系・求百分数挑战
What percentage of 300 is 75?
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百分比关系・求百分数基础
Isabel grows potatoes in her garden. This year, she harvested 760 potatoes and saved 10% of them to plant next year. How many of the harvested potatoes did Isabel save to plant next year?
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