Mental Math Strategies Jim Olsen Ph D for

The Zorro Strategy for Multiplying a Fraction Times a Number Steps: • Divide 4

The Zorro Strategy for Multiplying a Fraction Times a Number Example: 35 7 “Divide

The Zorro Strategy for Multiplying a Fraction Times a Number Try These: “Divide First,

The Zorro Strategy for Multiplying a Fraction Times a Number Answers: “Divide First, Multiply

The Front End Strategy When to use this strategy: Use this strategy when there

The Front End Strategy (a foundational strategy) Answers:

Five Keys for Learning Mental Math and The Top 6 Reasons Why Mental Math

The Divide by 5 Strategy by multiplying by 2 and dividing by 10 Examples:

The Divide by 5 Strategy by multiplying by 2 and dividing by 10 Try

The Divide by 5 Strategy by multiplying by 2 and dividing by 10 Answers:

The Teens Times Table Strategy When: Use this strategy when multiplying two numbers in

The Teens Times Table Strategy Try These:

The Teens Times Table Strategy Why does this work? Step b Step a Step

Use, or Make, Compatible Factors Strategy When: Use this strategy when multiplying numbers, one

Use, or Make, Compatible Factors Strategy Try These:

Use, or Make, Compatible Factors Strategy Answers:

Comments on the Strategies I Prefer I prefer strategies which: ØHave broad use. (They

When doing math, involving calculations, The Most Important Question to Ask (yourself and your

Equal Additions Strategy for Subtraction When: Use this strategy when subtraction would require regrouping

Equal Additions Strategy for Subtraction Try These:

Equal Additions Strategy for Subtraction Answers:

Multiplying Numbers Less than 100 Strategy Steps: a. Determine how far under 100 the

Multiplying Numbers Less than 100 Strategy Try These:

Multiplying Numbers Less than 100 Strategy Answers: Why does this work? …. left as

More Information… If you, or your students, want practice with the basic facts see

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Mental Math Strategies Jim Olsen, Ph. D. for WIU Math Club

The Zorro Strategy for Multiplying a Fraction Times a Number Steps: • Divide 4 into 24 (get 6) • Multiply 6 times 3 (get 18) 18 6 “Divide First, Multiply Second”

The Zorro Strategy for Multiplying a Fraction Times a Number Example: 35 7 “Divide First, Multiply Second”

The Zorro Strategy for Multiplying a Fraction Times a Number Try These: “Divide First, Multiply Second”

The Zorro Strategy for Multiplying a Fraction Times a Number Answers: “Divide First, Multiply Second”

The Front End Strategy When to use this strategy: Use this strategy when there is no regrouping (“carrying” with addition or “borrowing” with subtraction). How to use this strategy: This is a left-to-right strategy. Do it the way you say it.

The Front End Strategy Try These:

The Front End Strategy (a foundational strategy) Answers:

I’m assuming …

Five Keys for Learning Mental Math and The Top 6 Reasons Why Mental Math is Important and Useful https: //prezi. com/3 azgqq 64 xedo/keys-for-mental-math-learning-in-7 -12/

The Divide by 5 Strategy by multiplying by 2 and dividing by 10 Examples:

The Divide by 5 Strategy by multiplying by 2 and dividing by 10 Try These:

The Divide by 5 Strategy by multiplying by 2 and dividing by 10 Answers:

The Teens Times Table Strategy When: Use this strategy when multiplying two numbers in the teens (11 -19). How: Steps: a. Take one number and add the units digit of the other number. b. Tack on 0. c. Multiply the units digits. d. Add it on.

The Teens Times Table Strategy Try These:

The Teens Times Table Strategy Answers:

The Teens Times Table Strategy Why does this work? Step b Step a Step c Step d

Use, or Make, Compatible Factors Strategy When: Use this strategy when multiplying numbers, one of which ends in 5 and one is even. How: Pair up numbers to make the numbers easier to work with. Examples: 5 × 7 × 9 × 2 = (5 × 2) × (7 × 9) = 10 × 63 = 630 28 × 25 = 7 × (4 × 25) = 7 × 100 = 700 15 × 36 = (15 × 4) × 9 = 60 × 9 = 540 This works because of the Commutative and Associative properties of multiplication.

Use, or Make, Compatible Factors Strategy Try These:

Use, or Make, Compatible Factors Strategy Answers:

Comments on the Strategies I Prefer I prefer strategies which: ØHave broad use. (They can be used in many situations. ) ØBased on foundational mathematics and mathematical reasoning (e. g. , basic properties). ØAre not tricky to use. The Most Important Question to Ask (yourself and your students) is….

When doing math, involving calculations, The Most Important Question to Ask (yourself and your students) is…. Do we have a mental math strategy for this? If yes, use it. If no, (probably) use a calculator.

Equal Additions Strategy for Subtraction When: Use this strategy when subtraction would require regrouping (borrowing). How: Add a number to both numbers to make the number you are subtracting easy. This works because you are actually adding 0. Examples:

Equal Additions Strategy for Subtraction Try These:

Equal Additions Strategy for Subtraction Answers:

Multiplying Numbers Less than 100 Strategy Steps: a. Determine how far under 100 the two numbers are. b. Add these and subtract from 100 to get the first two digits of the answer. c. Multiply these to get the last two digits of the answer.

Multiplying Numbers Less than 100 Strategy Try These:

Multiplying Numbers Less than 100 Strategy Answers: Why does this work? …. left as an exercise for you.

More Information… If you, or your students, want practice with the basic facts see http: //faculty. wiu. edu/JR-Olsen/wiu/Boot. Camp/Basic. Training/ OR http: //www. multiplication. com/ I have written a curriculum for 7 th Grade, 8 th Grade, Algebra I, and (half of) Geometry. Each curriculum teaches 30 mental math strategies (15 for Geometry). Examples, practice, and mixed practice are included. See Course Specific Mental Math Curriculum at http: //faculty. wiu. edu/JR-Olsen/wiu/mentalmath/Course. Specific/front. html Questions ? (Distribute answers. )