**How do I Cross Multiply?**

Examples of Cross Multiplication

**Related Topics**

How do I make a mixed number into an improper fraction?

How do I simplify a fraction?

### Interactive Practice and Games:

Equivalent fractions (mixed numbers): http://www.sheppardsoftware.com/mathgames/fractions/memory_fractions4.htm

Board games (includes reducing fractions): http://www.math-play.com/adding-and-subtracting-fractions-game.html

Add fractions football: http://www.math-play.com/football-math-adding-fractions/football-math-adding-fractions.html

Fruit Shoot – Fraction Addition (different levels of difficulty): http://www.sheppardsoftware.com/mathgames/fractions/FruitShootFractionsAddition.htm

Challenge Board – pair fractions that add to 1: http://www.coolmath-games.com/0-fractone/index.html

Fraction Soccer (choose operation and level of difficulty): http://www.funbrain.com/fractop/index.html

**MCC5.NF.4** Apply and extend previous understandings of multiplication to multiply a fraction or whole number by a fraction.

a. Interpret the product (a/b) × q as a parts of a partition of q into b equal parts; equivalently, as the result of a sequence of operations a × q ÷ b.

For example, use a visual fraction model to show (2/3) × 4 = 8/3, and create a story context for this equation. Do the same with (2/3) × (4/5) = 8/15. (In general, (a/b) × (c/d) = ac/bd.)

b. Find the area of a rectangle with fractional side lengths by tiling it with unit squares of the appropriate unit fraction side lengths, and show that the area is the same as would be found by multiplying the side lengths. Multiply fractional side lengths to find areas of rectangles, and represent fraction products as rectangular areas.

**MCC5.NF.5** Interpret multiplication as scaling (resizing), by:

a. Comparing the size of a product to the size of one factor on the basis of the size of the other factor, without performing the indicated multiplication.

b. Explaining why multiplying a given number by a fraction greater than 1 results in a product greater than the given number (recognizing multiplication by whole numbers greater than 1 as a familiar case); explaining why multiplying a given number by a fraction less than 1 results in a product smaller than the given number; and relating the principle of fraction equivalence a/b = (n × a)/(n × b) to the effect of multiplying a/b by 1.

** MCC5.NF.6** Solve real world problems involving multiplication of fractions and mixed

numbers, e.g., by using visual fraction models or equations to represent the problem.

**MCC5.NF.7** Apply and extend previous understandings of division to divide unit fractions by whole numbers and whole numbers by unit fractions.1

a. Interpret division of a unit fraction by a non-zero whole number, and compute such quotients.For example, create a story context for (1/3) ÷ 4, and use a visual fraction model to show the quotient. Use the relationship between multiplication and division to explain that (1/3) ÷ 4 = 1/12 because (1/12) × 4 = 1/3.

1 Students able to multiply fractions in general can develop strategies to divide fractions in general, by reasoning about the relationship between multiplication and division. But division of a fraction by a fraction is not a requirement at this grade.

### How to:

#### MULTIPLY fractions:

**http://www.youtube.com/watch?v=XTHlf3MOiaM**

MODELING multiplication of fractions: http://www.youtube.com/watch?v=kNDgekqyChs

CROSS REDUCING: http://www.youtube.com/watch?v=Svm0igHraBs

Multiply MIXED NUMBERS:http://www.khanacademy.org/math/arithmetic/fractions/mixed_number_mult_div/v/multiplying–mixed-numbers

Calculate area with fractional side lengths with tiling: http://learnzillion.com/lessons/1542-find-the-area-of-a-rectangle-with-fractional-side-lengths-by-tiling

Multiplication of fractions as scaling: https://www.khanacademy.org/math/arithmetic/fractions/multiplying_fractions/v/multiplication-as-scaling

#### DIVIDE FRACTIONS:

Divide Fractions by Whole Numbers (models): http://learnzillion.com/lessons/3788-solve-problems-involving-division-of-unit-fractions-by-whole-numbers

Divide Whole Numbers by Fractions (models): http://learnzillion.com/lessons/1040-divide-whole-numbers-by-unit-fractions-using-a-model

### Interactive Practice and Games:

Dividing Fractions Basketball: http://www.math-play.com/math-basketball-dividing-fractions-game/math-basketball-dividing-fractions-game.html

Jeopardy: http://www.math-play.com/Fractions-Jeopardy/fractions-jeopardy.html

2-Player Game: http://www.counton.org/games/map-fractions/frosty/

Super-Brain Soccer: http://www.funbrain.com/cgi-bin/fract.cgi?A1=s&A2=10&A15=1

1 or 2 player challenge board: http://www.quia.com/cb/130255.html

Ratio’s are the same as fractions: http://www.arcademicskillbuilders.com/games/ratio-blaster/ratio-blaster.html

Dirt Bike (compare fractions): http://www.arcademicskillbuilders.com/games/dirt-bike-comparing-fractions/dirt-bike-comparing-fractions.html

GCF/LCM Flashcards: https://flashcards.engrade.com/mathgcflcmflashcards

**THE Fraction RAP: http://www.youtube.com/watch?v=43uGXipoVVQ

**Teacher Resources**

**Georgia Unit**

**Standard Tabs**

** Download 5th grade standards unit 4 tabs**

**Stickers**

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**Starter Ppt**