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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 - PowerPoint PPT Presentation
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Secrets ofSecrets ofMental MathMental Math
By: Katie Blumenstock
•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.
What is Mental Math?What is Mental Math?
What the practice of What the practice of Mental Math can do!Mental Math can do!
Adding NumbersAdding 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!
Adding NumbersAdding Numbers 47
+ 32 (30 + 2)
47 + 32→ 47 + 30 = 77 + 2 = 79
Multiplying by 9 Multiplying by 9
Multiplying By 11 Multiplying By 11
The Quicker Way
3+2 = 5 1. Take the first factor and add the two numbers together.
2. Split the first factor and place the sum of the factor in the middle
352
Examples 23 x 1145 x 11 27 x 11
Examples Examples 23 x 11 = 25345 x 11 = 495 27 x 11 = 297
There’s an Exception to There’s an Exception to Every RuleEvery Rule
• If the sum of the first factor is greater than 10, you simply carry over…
(6 + 7 = 13)1
+ 637 737
2-by-1 2-by-1 MultiplicationMultiplication
42 x 7
The Quicker Way42x 7
(40 + 2) 1st Break up the first factor
2nd Multiply the small multiplication tasks
40 x 7 = 280 2 x 7 = 14
3rd Add both of the small multiplication tasks together
Examples Examples
87 x 5
38 x 9
Examples 87 x 5
38 x 9
(80 + 7)
80 x 5 = 4007 x 5 = 35400 + 35 = 435
(30 + 8)
30 x 9 = 2708 x 9 = 72 270 + 72 = 342
OverviewOverview• 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
References
• Benjamin, Arthur and Shermer, Michael. “Secrets of Mental Math.” Lowell House (2006).
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