MATH TRICK - MULTIPLYING BY 9

 

To multiply by 9 quickly, you can use a simple trick:

1. Single-Digit Numbers: For numbers 1 through 9, multiply the number by 10 and then subtract the original number. For example:

   • $4 \times 9 = (4 \times 10) - 4 = 40 - 4 = 36$.

2. Pattern for 1 to 9: Each result has digits that add up to 9.

   • $2 \times 9 = 18$ (1 + 8 = 9)
   • $6 \times 9 = 54$ (5 + 4 = 9)

3. Multiplying Larger Numbers: Break the number into parts. For example:

   • $23 \times 9$ can be split into $(20 + 3) \times 9 = (20 \times 9) + (3 \times 9) = 180 + 27 = 207$.