Here’s an example of a SPEED MATH shortcut for MULTIPLYING 4-DIGIT NUMBERS NEAR A BASE NUMBER : (Mul) NrB4 from the MULTIPLICATION category.
When can I use this method?
For multiplying any 4-digit number with another 4-digit number such that the numbers are relatively near each other.
You may also use this method to multiply numbers a little farther away from each other as long as their differences from the Base number are easy to multiply.
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- When selecting a Base number, prefer a number that is near the multiplier and multiplicand as well as it should be easy to multiply with (prefer round numbers).
- This method uses the concept (B + a) (B + b) = [(B + a) + b] + ab or [(B + b) + a] + ab, where ‘(B + a)’ and ‘(B + b)’ are numbers near a Base number ‘B’ and ‘a’ and ‘b’ are the respective differences.
- Whenever the number is more than the Base number, the difference is written as positive (+ve).
- Whenever the number is less than Base Number, the difference is written as negative (-ve).
- When both numbers are either less or more than Base Number, you add the product of differences.
- When one number is more than Base number and another less than Base number, you subtract the product of differences.
Related Shortcuts –
Multiplying 2-digit Numbers near a Base Number: (Mul) NrB2
Multiplying 3-digit Numbers near a Base Number: (Mul) NrB3
Multiplying Numbers near different Base Numbers: (Mul) NrBpBs
Multiplying Numbers using Nearby Method: (Mul) NxM(Nr)