Speedy Math 2 – Transformation in Addition and Subtraction

Addition of two single digit numbers is easy. It becomes more difficult when the numbers contain more digits. In these cases, changing the number(s) first to an equal form can make the calculation much easier.

For example, 198 + 277
Step 1: 198 = 200 – 2
Step 2: 200 + 277 = 477 (or 277 – 2 = 275)
Step 3: 477 - 2 = 475 (or 200 + 275 = 475)

Another example, 673 – 395
Step 1: 395 = 400 – 5
Step 2: 673 – 5 = 668
Step 3: 400 + 668 = 1068