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Common Mistakes

T O T O
3 5 3 5

+ 3 + 3

6 5  3 8 

Example 2. Add: 50 + 4.
Solution.

Step 1. Add the ones. Step 2. Add the tens.

T O T O

5 0 5 0

+ 4 + 4

4 5 4

Thus, 50 + 4 = 54. Tips

We can add a 2-digit number and a 1-digit
Example 3. Add 43 and 6. number by breaking up the numbers.
Solution.

Step 1. Break the bigger number Step 2. Now, add the ones.

into tens and ones. 43 + 6 = 40 + 3 + 6
43 = 40 + 3 = 40 + 9

Step 3. Then, add the tens and the ones.

40 + 9 = 49
Thus, 43 + 6 = 49.

Exercise 7A

1. Solve the following using the number strips.

a. 28 + 4 = b. 29 + 7 = c. 31 + 9 =

d. 26 + 5 = e. 32 + 6 =

21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40

107
Addition and Subtraction up to 100