Secrets of Mental 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 the practice of Mental Math can do!

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

(30 + 2) → = = 79

Multiplying by 9

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

Examples 23 x x x 11

Examples Examples 23 x 11 = x 11 = x 11 = 297

There’s an Exception to Every Rule If the sum of the first factor is greater than 10, you simply carry over… (6 + 7 = 13)

2-by-1 Multiplication 42 x 7

The Quicker Way 42 x 7 42 x 7 (40 + 2) 1 st Break up the first factor 2 nd Multiply the small multiplication tasks 40 x 7 = x 7 = 14 3 rd 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 = x 5 = = 435 (30 + 8) 30 x 9 = x 9 = = 342

Overview There are many more tricks to Mental Math –F–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).