Here’s an example of a SPEED MATH shortcut for MULTIPLYING NUMBERS WITH FIRST DIGITS SUM 1000 : (Mul) F1000dx from the MULTIPLICATION category.

When can I use this method?
For multiplying any 4-digit number with another 4-digit number such that the sum of the initial digits of the multiplier and multiplicand = 1000 and the remaining digits of multiplier are same as that of the multiplicand.
For multiplying any 5-digit number with another 5-digit number such that the sum of the initial digits of the multiplier and multiplicand = 1000 and the remaining digits of multiplier are same as that of the multiplicand.
You cannot use this method to multiply numbers with unequal number of digits, i.e. multiplying a 4-digit number with a 5-digit number.
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