Multiplying Three digit Numbers with Middle digit 4

1. Select a 3-digit number with a middle digit of 4 (last digit not zero).
2. Choose a multiplier with the same first two digits, whose third digit sums to 10 with the third digit of the first 3-digit number.
3. The last three digits will be 0 and the product of the third digits: _ _ _ 0 X X.
4. The third digit from the right will be 9 times the first digit + 2 (keep the carry): _ _ X _ _.
5. The first two digits will be the square of the first digit plus the carry: X X _ _ _ _.

As you determine the digits in the answer from right to left, repeat them to yourself at each step until you have the whole answer.

Example:

1. If the first number is 541, choose 549 as the second number (same first digits, third digits add to 10).
2. Last three digits: 0 and the product of the third digits:
   1 × 9 = 9: _ _ 0 0 9
3. Next digit: 9 times the first digit + 2:
   9 × 5 = 45, 45 + 2 = 47 (keep carry 4):
   _ _ 7 _ _ _
4. First two digits: square the first and carry:
   5 × 5 = 25, 25 + 4 = 29: 2 9 _ _ _ _
5. So 541 × 549 = 297009.