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Secrets of Mental Math

Secrets of Mental Math. “Lighting Calculations and Tricks”. By: Katie Blumenstock. What is Mental Math?. Calculations that are either done mentally or with pencil or paper. They are tricks to solve what looks to be difficult math equations Committed to memory

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Secrets of Mental Math

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  1. Secrets ofMental Math “Lighting Calculations and Tricks” By: Katie Blumenstock

  2. What is Mental Math? • Calculations that are either done mentally or with pencil or paper. • They are tricks to solve what looks to be difficult math equations • Committed to memory • Multiplication, Division, or Double facts.

  3. What the practice of Mental Math can do!

  4. Adding Numbers • From 1st Grade, You were always told to add… RIGHT TO LEFT! THEY WERE WRONG!! Adding from Left to Right is the Simplest and Quickest Way!

  5. Adding Numbers 47 + 32 (30 + 2) 47 + 32→ 47 + 30 = 77 + 2 = 79

  6. Multiplying by 9 The easiest way to multiply by 9 is by using your HANDS

  7. Multiplying By 11 32 x 11

  8. The Quicker Way 3+2 = 5 • Take the first factor and add the two numbers together. • Split the first factor and place the sum of the factor in the middle 32 x 11 352

  9. Examples  23 x 11 45 x 11 27 x 11

  10. Examples  23 x 11 =253 45 x 11 =495 27 x 11 =297

  11. There’s an Exception to Every Rule • If the sum of the first factor is greater than 10, you simply carry over… 67 x 11 (6 + 7 = 13) 1 + 637 737

  12. 2-by-1 Multiplication 42 x 7

  13. The Quicker Way 42 x 7 (40 + 2) 1st Break up the first factor 40 x 7 = 280 2 x 7 = 14 2nd Multiply the small multiplication tasks 3rd Add both of the small multiplication tasks together 280 + 14 = 294

  14. Examples  87 x 5 38 x 9

  15. Examples  87 x 5 38 x 9 (80 + 7) (30 + 8) 80 x 5 = 400 7 x 5 = 35 400 + 35 = 435 30 x 9 = 270 8 x 9 = 72 270 + 72 = 342

  16. Overview • There are many more tricks to Mental Math • Figuring out the week of any date in the past • Andriod and IPhone apps • Book by “Secrets of Mental Math” By Arthur Benjamin and Michael Shermer

  17. References • Benjamin, Arthur and Shermer, Michael. “Secrets of Mental Math.” Lowell House (2006).

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