Page 191 - Start Up Mathematics_3

Example 4: Find 9 × 8.

Solution: 9 is 1 less than 10.

8 is 2 less than 10.

Deficiencies

9 1 9 – 2 = 7

× 8 2 8 – 1 = 7 So, the digit in the tens place = 7
7 2 2 × 1 = 2 The digit in the ones place = 2

So, 9 × 8 = 72.

Example 5: Find 7 × 6

Solution: 7 is 3 less than 10.

6 is 4 less than 10.
Deficiencies

7 3 7 – 4 = 3

× 6 4 6 – 3 = 3 So, the digit in the tens place = 3

4 2 3 × 4 = 1 2
Since 12 is a two-digit number, we keep the 2 and
carry 1 to the tens place and add it to 3.

So, the digit in the tens place = 3 + 1 = 4 and the
digit in the ones place = 2.

Thus, 7 × 6 = 42.

Try these: 8 × 7, 6 × 5, 6 × 6, 7 × 7

(b) Two numbers close to 100

Example 6: Find 88 × 98.

Solution: 88 is 12 less than 100.
98 is 2 less than 100.

Deficiencies

8 8 1 2 88 – 2 = 86 86 becomes the first part of the

× 9 8 2 98 – 12 = 86 answer.

8 6 2 4 12 × 2 = 24 24 becomes the second part of the
So, 88 × 98 = 8624. answer.
Try these: 87 × 98, 86 × 94, 75 × 87, 92 × 65

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