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Lesson 1-3: Mult/Div Real #s. The first slides here review adding, subtracting, multiplying, and dividing fractions. You do not have to take notes on these slides. We will do a few practice problems in class. Add & Subtract Fractions. Find the common denominator.
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Lesson 1-3: Mult/Div Real #s The first slides here review adding, subtracting, multiplying, and dividing fractions. You do not have to take notes on these slides. We will do a few practice problems in class.
Add & Subtract Fractions • Find the common denominator. • Make equivalent fractions using the new common denominator. • Add/sub the numerators. Denominator stays the same. • Simplify/reduce. • Leave improper fractions as is. Hooray!
Examples 1
Multiply Fractions & Mixed #s • Change any mixed #s into improper fractions. • Multiply numerators. • Multiply denominators. • Simplify. (You can also simplify before you multiply.) • Leave improper fractions as is.
Examples 1 2 2 1
Divide Fractions & Mixed #s • Change any mixed #s into improper fractions. • Find the reciprocal of the 2nd fraction (the divisor), rewriting the problem as a multiplication problem. • Multiply. • Simplify. (You can also simplify before you multiply.) • Leave improper fractions as is.
Examples 1 2 8 5
Decimal Operations - Reminders • Multiplication • Line up digits as in whole # mult. • After multiplying as usual, count up total places behind decimal point, and move decimal that number of places.
Decimal Operations - Reminders • Division: • Shift decimal in the divisor (outside #) to the right so that you are dividing by a whole #. Shift the decimal in the dividend the same # of places. Now divide as usual. • Keep dividing until it ends or repeats.
Now in your Know It Notes: • Reciprocal: numerator and denominator change place (fraction flipped over) • Multiplicative inverse: a number and its reciprocal are called multiplicative inverses • A number times its reciprocal = 1
Inverse Prop. Of Multiplication • The product of a real # (but not zero) and its reciprocal is 1. • Algebraically: For a≠0,
Integer Rules • Positive # • Positive # = Positive # • Negative # • Negative # = Positive # (Same signs = positive answer) • Positive # • Negative # = Negative # • Negative # • Positive # = Negative # (Opposite signs = neg answer) • Same rules for division.
Important Stuff about Zero • Zero times a number = zero • Zero divided by a number = zero • A number divided by zero = undefined • How could you make zero groups of something? It is not possible, so we get “undefined” instead.