Multiplication Trick: Multiply Any Number by 9 Quickly

 

Introduction

Multiplying by 9 can be done quickly using a simple Mental Math trick. Instead of direct multiplication, you can multiply by 10 and then subtract the original number.

This method is fast, accurate, and useful in everyday calculations.

The Trick

To multiply a number by 9:

Formula

Number × 9

= (Number × 10) − Number

Example 1

Find:

7 × 9

Solution

7 × 10 = 70

70 − 7 = 63

Answer

63

Example 2

Find:

12 × 9

Solution

12 × 10 = 120

120 − 12 = 108

Answer

108

Example 3

Find:

25 × 9

Solution

25 × 10 = 250

250 − 25 = 225

Answer

225

Example 4

Find:

38 × 9

Solution

38 × 10 = 380

380 − 38 = 342

Answer

342

Example 5

Find:

56 × 9

Solution

56 × 10 = 560

560 − 56 = 504

Answer

504

Practice Questions

Try these yourself:

  1. 15 × 9

  2. 24 × 9

  3. 42 × 9

  4. 63 × 9

  5. 81 × 9

Answers

  1. 135

  2. 216

  3. 378

  4. 567

  5. 729

Key Learning

Since:

9 = 10 − 1

Multiplying by 9 becomes:

(Number × 10) − Number

This method is often faster than traditional multiplication.

Practice Tip

Practice the multiplication tables of 9 from:

9 × 1 to 9 × 20

Then use the ×10 − Number shortcut for larger calculations.

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