Use compensation to subtract: up to three digits
🛝 Subtraction compensation is a magic trick! If you slide BOTH numbers by the same amount, the difference stays the exact same.
Do this: Read the concept below, then try the quiz or activity.
Concept
Subtraction is about finding the difference (or distance) between two numbers. If you move both numbers the same amount on a number line, the distance between them doesn't change!
🎯 How Subtraction Compensation Works: Unlike addition, in subtraction, you do the SAME thing to both numbers to keep the distance equal. Example: 500 - 198 = ? 198 is an ugly number to subtract. Let's make it a friendly 200. 1. Shift the Number: Add +2 to 198 to make it 200. 2. Shift the Other Number: You MUST add +2 to 500 to keep the distance the same! (It becomes 502). 3. The New Problem: 502 - 200. 4. Subtract the Friendly Numbers: 502 - 200 = 302! So, 500 - 198 = 302.
Try it
Slide the numbers to make the subtraction easy!
Instructions: Shift BOTH numbers by the same amount to create a friendly problem.
Problem 1: 400 - 199 * Add +1 to 199 to make 200. * Add +1 to 400 to make 401. * 401 - 200 = ___
Problem 2: 350 - 98 * Add +2 to 98 to make ___. * Add +2 to 350 to make ___. * Answer: ___
Problem 3: 600 - 295 * Answer: ___
Problem 4: 810 - 390 * (Hint: add +10 to both!) * Answer: ___