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Deb Russell

Black Friday Math

By November 22, 2012

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What is Black Friday Math? It's the mental math that many individuals will likely be doing as they quickly calculate the 40% or 25% off of the ticketed price. The strategies to compute saving are varied and of those individuals I asked, they all used a different strategy! For instance, let's say you get 75% off an $80.00 item. Here is how some individuals do their mental math:

  • I know that 50% of 80 is 40. 25% is half of 50%. Since 50% was 40, then 25% must be half of that or 20. Then I added 40 and 20 and I got 60.
  • I know that 10% of 80 is 8. In order to get 70%, I multiplied 8x7 and got 56. I still need 5% more. I thought 5% is half of 10%, so 5% must be 4. By adding 56 and 4, I got 60.
  • I know that 75% is the same as . I divided 80 into fourths. Each fourth is 20. Three of them make 60.
  • I changed 75% to 0.75 and multiplied. 0.75 x 80 is 60.
  • I know how to find 1%. Move the decimal 2 places to the left. 1% of $80.00 is 0.8 75% is 75 x 0.8 which is 60
  • I know that if I get 75% off $80.00 $80.00 = 100% I must pay 100% less 75% which is 25% Therefore of 80 = 20.00 and $80.00 - $20= $60.00

Somehow, I just know there are still more strategies than those listed above. If you use something different, please share yours. Although most of us like to find the most efficient strategy, what may feel efficient to us doesn't always feel like the most efficient method to somebody else.
Happy Black Friday Shopping!

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