Mental Multiplication of 2 digits by 2 digits

Mentally multiplying one digit by one digit is simple (normally memorising the answers).

How about mentally multiplying 2 digits by one digit? Maybe OK.

Principle of 2 digit by one digit mental multipication:
- Expand the 2 digit to include a 10's number.

Example: 45 ==> 40 + 5

Let's do an example: 45 x 6

Mental solution: (40 + 5) x 6 ==> (40 x 6) + (5 x 6) ==> 240 + 30 ===> 270 (ANSWER)

Mentally multiplying 2 digit by 2 digit ?

Can also be done using the same splitting math principle.

Example: 45 x 12

Mental Solution
Step 1: Split the 45 to (40 + 5)
Step 2: Perform 40 x 12 ==> 10 x 4 x 12 ==> 10 x 48 ==> 480
Step 3: Perform 5 x 12 ==> 60
Step 4: Add up the above 2 results, 480 + 60 = 540 (ANSWER)

Concept:
Split the original to the 10's number and use addition instead of direct multiplication.

Just remember that it is always easier to manage 10's multiplication and addition.

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