Addition & Subtraction
加法與減法
Addition puts things together and subtraction takes them away. In this lesson you will learn how to add, subtract, use number bonds, and add bigger numbers using the column method.
加法把東西放在一起，減法把東西拿走。在這一課，你會學習怎樣加、減、使用數字組合，以及用直式計算較大的數字。
1 · What is addition?
甚麼是加法？
Addition means putting two groups together to find the total. When you add 3 apples and 2 apples, you get 5 apples. We write this as 3 + 2 = 5. The answer is called the sum.
加法是把兩組東西放在一起，找出總數。把 3 個蘋果和 2 個蘋果放在一起，就有 5 個蘋果。我們寫作 3 + 2 = 5。答案稱為「和」。
2 · What is subtraction?
甚麼是減法？
Subtraction means taking away. When you have 5 apples and take away 2, you are left with 3. We write this as 5 − 2 = 3. The answer is called the difference.
減法是指拿走一些。有 5 個蘋果，拿走 2 個，剩下 3 個。我們寫作 5 − 2 = 3。答案稱為「差」。
3 · Number bonds to 10
十的數字組合
Number bonds are pairs of numbers that add up to 10:
數字組合是加起來等於 10 的一對數字：
- 4 + 6 = 104 加 6 等於 10。
- 7 + 3 = 107 加 3 等於 10。
- 5 + 5 = 105 加 5 等於 10。
- 1 + 9 = 101 加 9 等於 10。
Number bonds to 10 help you add and subtract quickly.
十的數字組合能幫助你快速計算加減。
4 · The column method
直式計算
For bigger numbers, we use the column method. Write the numbers one above the other, lining up the ones and the tens, then add or subtract each column from the right.
對於較大的數字，我們用直式計算。把數字上下對齊，個位對個位、十位對十位，然後由右邊開始逐欄相加或相減。
Line up the ones and tens, then work from right to left.
對齊個位和十位，然後由右至左計算。
5 · Quick check
小測驗