How to Multiply Any Two-Digit Number by 11 in 3 Seconds Without a Calculator

I well come you  all to brainimatic Series lesson, here I will teach you how to multiply 2 and 3 digits numbers by 11 with using calculator or before 4 seconds. This a kind of brain box mathematics and so called mental Mathematics.

Multiplying numbers by 11 in your head doesn't require a calculator or long multiplication. By using a simple mental math trick in which brainimatic Series will give you the concept as a  students, you can find the exact answer to any two 2 digits multiplication by 11 in less than 3 seconds without using calculator or showing working.

As a WAEC and NECO examination might occured, that involves multiplying 46 by 11 this can be applied in the main sense to get a quick answer.

The Main Trick: "The Separation and Sum Method"

Here is are ways to manipulate  (multiply) any two given digit number by 11, follow these two simple steps:

• Step 1: Separate the two digits of the number and leave a space in the middle.
• Step 2: Add the two digits together and place the sum in that middle space. (If the sum is 10 or greater than, simply carry over the 1 to the first digit) (As renamef).

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Example 1: Basic Trick (No Carry Over)

Problem: Evaluate 15 × 11

Solution:

1. Separate the digits 3 and 5, leaving a space: 1 ( ) 5
2. Add the two digits together: 3 + 5 = 8
3. Place the 8 in the middle space: 3(6)5

Final Answer: 35 × 11 = 365

This is so simple to understand.

Example 2: Low Numbers Case

Problem: Calculate 14 × 11

Solution:

1. Separate the digits 1 and 4: 1 ( ) 4
2. Add the digits together: 1 + 4 = 5
3. Put 5 in the center space: 1( 5 ) 4

Final Answer: 14 × 11 = 154

Example 3: Middle Range Numbers

Problem: Calculate 62 × 11

Solution:

1. Separate the digits 6 and 2: 6 ( ) 2
2. Add the digits together: 6 + 2 = 8
3. Put 8 in the center space: 6 ( 8 ) 2

Final Answer: 62 × 11 = 682

Example 4: The Carry Over Rule (Sum Equals 10)

Problem: Calculate 46 × 11

Solution:

1. Separate the digits 4 and 6: 4 ( ) 6
2. Add the digits together: 4 + 6 = 10
3. Since the sum is a two-digit number (10), put the 0 in the middle and carry the 1 over to the first digit (4 + 1 = 5).

Final Answer: 46 × 11 = 506

Example 5: High Numbers with Carry Over

Problem: Calculate 75 × 11

Solution:

1. Separate the digits 7 and 5: 7 ( ) 5
2. Add the digits together: 7 + 5 = 12
3. Put the 2 in the middle and carry the 1 over to the first digit (7 + 1 = 8).

Final Answer: 75 × 11 = 825

Example 6: Tricky Large Digit Carry Over

Problem: Calculate 89 × 11

Solution:

1. Space the digits 8 and 9: 8 ( ) 9
2. Add the digits together: 8 + 9 = 17
3. Put the 7 in the middle and carry the 1 over to the first digit (8 + 1 = 9).

Final Answer: 89 × 11 = 979

Example 7: The Maximum Two Digit Pattern 

Problem: Calculate 99 × 11

Solution:

1. Separate the digits 9 and 9: 9 ( ) 9
2. Add the digits together: 9 + 9 = 18
3. Put the 8 in the middle and carry the 1 over to the first digit (9 + 1 = 10).

Final Answer: 99 × 11 = 1089

Class Work 

Evaluate the following:

(a) 13 x 11

(b) 17 x 11

(c) 87 x 11

By practicing this "Separation and Sum" mental shortcut, you will never need to pull out a phone calculator for basic base 11 mathematics multiplication again.I hope the lesson will help you in mental mathematics or in examination. You're free to ask any question.