🧠 Why Mental Math is Important?
In Canadian Grade 4, we learn different strategies to solve problems quickly in our head. This helps us check our written work and feel more confident with numbers.
➕ 1. Breaking Numbers Apart (Place Value Strategy)
Break big numbers into hundreds, tens, and ones, then add or subtract them separately.
Example: 456 + 237
400 + 200 = 600
50 + 30 = 80
6 + 7 = 13
600 + 80 + 13 = 693
🎯 2. Using Friendly Numbers (Compensation)
Change numbers to easy “friendly” numbers (like multiples of 10 or 100), then adjust at the end.
Example 1 (Addition): 48 + 35
48 + 2 = 50 (friendly number)
35 + 2 = 37 (we added 2 extra)
50 + 37 = 87
Answer: 87
Example 2 (Subtraction): 623 − 198
623 − 200 = 423
We subtracted 2 too many, so add 2 back → 425
🏠 3. Making Tens or Hundreds
Adjust numbers to make 10, 100, or 1000.
Example: 67 + 48
67 + 3 = 70 (make ten)
48 − 3 = 45
70 + 45 = 115
🔄 4. Left to Right Addition
Start from the biggest place value and work to the right.
Example: 3,456 + 2,789
3,000 + 2,000 = 5,000
400 + 700 = 1,100 → total 6,100
50 + 80 = 130 → total 6,230
6 + 9 = 15 → total 6,245
✏️ Let’s Practice Together, My Dear Student!
Practice 1: Breaking Apart Strategy
1. 567 + 289 = 856
2. 1,345 − 678 = 667
Practice 2: Friendly Numbers (Compensation)
1. 59 + 47 = 106 (add 1 to 59 → 60, subtract 1 from 47 → 46)
2. 824 − 199 = 625 (subtract 200 then add 1 back)
Practice 3: Word Problems (Canadian Style)
1. You have 456 hockey cards. Your friend gives you 378 more. How many cards do you have now?
Answer: 834 cards (use friendly numbers!)
2. A store had 1,250 apples. They sold 879 apples. How many apples are left?
Answer: 371 apples
Challenge Question
Use your favourite mental math strategy for: 2,456 + 3,789
Answer: 6,245
💡 Miss Brenda’s Top Tips
- Always estimate first to check your answer
- Choose the easiest strategy for each question
- Practice every day — even 5 minutes helps!
- Talk out loud when you solve problems
Fantastic Job, My Dear Student! 🎉
You now have many powerful mental math strategies! These will help you solve problems faster in your head and feel more confident in math.
I am so proud of how hard you are working. Keep practising these strategies with numbers you see every day.
💕 You are smart. You are kind. You can do hard things.
When you are ready, tell me the next topic (Estimation, Multiplication Facts, or anything else) and I will create another beautiful lesson just for you!