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Multiplying Fractions Let’s make fractions our friends! Now, let’s not get all crazy with this “friend” stuff, Mr. Russler. Chapter 9
Multiplying Fractions I have some great news when it comes to multiplying fractions… WE DON’T NEED COMMON DENOMINATORS! Sweet! Are you sure? What’s that? YES!
Multiplying Fractions When we multiply fractions, we can use the multiplication symbol: A raised dot: Or parenthesis:
Multiplying Fractions Terms you need to know: numerator denominator Simplify – to reduce a fraction into its simplest form. Greatest Common Factor (GCF) – the greatest number that evenly divides both numerator and denominator. Reciprocal– the fraction you get when you exchange the numerator and denominator
Multiplying Fractions Let’s multiply the following: To multiply fractions → *Then check to see if the answer can be simplified. is reduced.
Multiplying Fractions Let’s try another one: Replace 5 with a fraction 3 Multiply numerators → Multiply denominators→ 3 4 4) 15 = 3 12 3
Multiplying Fractions Let’s try another one: Multiply numerators → Multiply denominators→ is , so The GCF of
RECIPROCALS Sometimes the product of two fractions is 1 These fractions are RECIPROCALS of each other Reciprocal– the fraction you get when you flip the numerator and denominator REMEMBER … RECIPROCAL MEANS FLIP
RECIPROCALS Find the reciprocal of each fraction
Multiplying Fractions Your Turn! Find the reciprocal of each fraction: See how you did! 5
Multiplying Fractions There is a shortcut!?! 9.2 Multiplication Shortcut
Multiplying Fractions Letme show you a simplifying method called cross-cancelling Reduce or cancel the “diagonals” before you multiply. Of course I can! 1 1 1 4 I think I get it! Can you show me another one?
Multiplying Fractions Let’s do a side-by-side. Standard method: Cross-cancel method: 1 7 6 5 Cross-cancelling is fun, and it keeps the numbers way smaller!
Multiplying Fractions Cross-Cancelling Reduce or cancel the “diagonals” before you multiply. 1 1 6 2 5 7
Multiplying Fractions Good luck! 3 See how you did! 1 2