Mathematics - Term 3 - Week 9

Addition is the process of finding the total or sum by combining two or more numbers. For example, if you have 3 apples and you get 2 more, you can find the total by adding 3 + 2, which equals 5 apples. On the other hand, subtraction is the process of taking one number away from another. For instance, if you have 5 apples and you give away 2, you can find out how many you have left by subtracting 2 from 5, which equals 3 apples. Both operations are fundamental in mathematics and are often used in everyday situations.

Let's look at the problem: 47 + 36. To solve this, we can break it down into parts. First, add the tens: 40 + 30 = 70. Next, add the units: 7 + 6 = 13. Now, combine these results: 70 + 13 = 83. Therefore, 47 + 36 = 83.

Consider the problem: 92 - 28. We can also break this down. First, subtract the tens: 90 - 20 = 70. Then, subtract the units: 2 - 8. Since we cannot subtract 8 from 2, we need to borrow 1 from the tens, making it 12 - 8 = 4. Now, combine the results: 70 + 4 = 64. Thus, 92 - 28 = 64.

Let's work on these problems as a class. First, try 58 + 27. Start by adding the tens: 50 + 20. What do you get? Now, add the units: 8 + 7. Combine your answers. Next, let's do 75 - 19. Subtract the tens first: 70 - 10. Then, subtract the units: 5 - 9. Remember to borrow if needed! Share your answers with your partner and discuss your strategies.

Now it's your turn! Solve the following problems independently: 34 + 49, 86 - 37, 21 + 68, and 90 - 45. Remember to show your work clearly. After you finish, review your answers and check if you made any mistakes. If you did, think about how you can correct them.

• 42
• 52
• 32
• 40

Answer: 42

25 + 17 equals 42 because 20 + 10 = 30 and 5 + 7 = 12, so 30 + 12 = 42.

• 35
• 45
• 55
• 25

Answer: 35

64 - 29 equals 35 because 64 - 20 = 44 and 44 - 9 = 35.

Answer: 84

Adding 48 and 36 gives you 84.

Answer: 44

Subtracting 56 from 100 results in 44.

• 82
• 92
• 72
• 94

Answer: 92

73 + 19 equals 92 because 70 + 10 = 80 and 3 + 9 = 12, so 80 + 12 = 92.

• 38
• 48
• 28
• 58

Answer: 38

85 - 47 equals 38 because 85 - 40 = 45 and 45 - 7 = 38.

Answer: 85

Adding 29 and 56 gives you 85.

Answer: 38

Subtracting 34 from 72 results in 38.