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Example 12: Add 87 and 94. Top Tip

Solution: Round off 94 to 90. (94 – 90 = 4) You may select the
addend you find easier to
Add 90 to 87. round off and then correct

87 + 90 = 177 the sum accordingly.

As we added 4 less than 94, correct the answer by adding 4 to 177.

So, 177 + 4 = 181.

Exercise 2.5

Add the given numbers mentally using both methods to see which one you find easier.

(a) 46 + 33 (b) 62 + 47 (c) 56 + 74 (d) 25 + 34 (e) 59 + 30

Review Exercise

1. Add the given numbers.

(a) H T O (b) H T O (c) H T O

3 5 6 1 7 8 2 5 6
+ 7 2 + 2 3 + 4 9

(d) H T O (e) H T O (f) H T O
1 4 6 3 4 2 6 2 0

+ 2 0 3 + 1 5 7 + 1 4 9

(g) H T O (h) H T O (i) H T O
7 9 2 1 4 3 1 9 2

1 0 8 4 2 1 5 7 2
+ 9 9 + 2 5 4 + 2 8

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