Percentages (II)
One amount as a percentage of another; a percentage of an amount; the percentage that is left; the amount after an increase or decrease of a percentage; comparing the rates of two groups; estimating answers; and word problems. As the curriculum sets out, this topic leaves out discounts, interest and harder percentage changes such as "from 100 to 120 is an increase of what per cent"; finding the original amount comes in Simple equations (II).
Key words
| Chinese | English |
|---|---|
| 百分率 | percentage (rate) |
| 增加 | increase |
| 減少 | decrease |
| 估算 | estimate |
The 7 short lessons and the chapter test
Lessons are in Chinese for now.
- 求百分之幾
- 求一個數的百分之幾
- 增加和減少百分之幾
- 比較百分數
- 估算
- 應用題
- 綜合練習
- 章節測驗 (chapter test)
Sample questions (in Chinese)
Question 1一盒朱古力有 40 粒，已吃了 21 粒。已吃的佔全盒的百分之幾？
%
Answer and explanation
答案：52.5%
為甚麼？求 21 是 40 的百分之幾：2140 × 100% = 52.5%。
Question 2某屋苑有 60 戶，其中 75% 養寵物。養寵物的有多少戶？
戶
Answer and explanation
答案：45 戶
為甚麼？求 60 的 75%：60 × 75% = 60 × 75100 = 45。
Question 3一本書有 580 頁，小明已看了 60%。還有多少頁未看？
頁
Answer and explanation
答案：232 頁
為甚麼？未完成的部分佔 100% − 60% = 40%。580 × 40% = 232。也可以先求已完成的：580 × 60% = 348，580 − 348 = 232。
Question 4某校去年有 320 名學生，今年增加了 45%。今年有多少名學生？
名
Answer and explanation
答案：464 名
為甚麼？增加的部分：320 × 45% = 144；增加後：320 + 144 = 464。也可以這樣計算：320 × (100% + 45%) = 320 × 145% = 464。
Based on learning unit 6N4 of the Education Bureau’s Primary Mathematics Curriculum (2017).