Fast Calculation Trick for Multiplying by 11

 

Introduction

Mental Math techniques help you perform calculations quickly without a calculator. One of the easiest tricks is multiplying a two-digit number by 11.

The Trick

For a two-digit number:

AB × 11

  1. Add A and B.

  2. Place the sum between A and B.

Example:

23 × 11

2 + 3 = 5

Answer = 253

Example 1

24 × 11

Step 1:

2 + 4 = 6

Step 2:

Place 6 between 2 and 4

Answer = 264

Example 2

35 × 11

Step 1:

3 + 5 = 8

Step 2:

Place 8 between 3 and 5

Answer = 385

Example 3

42 × 11

Step 1:

4 + 2 = 6

Step 2:

Place 6 between 4 and 2

Answer = 462

Example 4

63 × 11

Step 1:

6 + 3 = 9

Step 2:

Place 9 between 6 and 3

Answer = 693

Example 5

81 × 11

Step 1:

8 + 1 = 9

Step 2:

Place 9 between 8 and 1

Answer = 891

Practice Questions

Try these yourself:

  1. 32 × 11

  2. 54 × 11

  3. 71 × 11

  4. 26 × 11

  5. 43 × 11

Answers

  1. 352

  2. 594

  3. 781

  4. 286

  5. 473

Key Learning

Mental Math is about recognizing patterns. The more patterns you learn, the faster your calculations become.

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