Créer une présentation
Télécharger la présentation

Télécharger la présentation
## Fractions Review:

- - - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - - -

**Fractions Review:**How to add, subtract, multiply and divide fractions and mixed numbers Compiled and adapted by Lauren McCluskey from several power points by Monica Yuskaitis**This power point would not have been possible without Monica**Yuskaitis.**Parts of a Fraction**3 = numerator = denominator 4 By Monica Yuskaitis**Parts of a Fraction**3 = numerator = denominator 4 = dividend 3 = divisor 4 Which means…3÷4 By Monica Yuskaitis**¾ looks like**Or 75% of the whole 1/4 1/4 1/4 If you think about money, ¾ of a dollar equals $0.75 or 75 cents. By Monica Yuskaitis**Or ¾ might look like:**1/4 0.25ft. 1/4 0.25ft 75% of the whole 1/4 0.25ft 0.25ft If the rectangle is 1 foot high, then each section is 0.25 ft. By Monica Yuskaitis**How much of 4 is 3?**• To find how big a portion you have, divide the numerator by the denominator. 3÷4 = 0.75 or 75% So ¾ = 75%**How many quarters are in a whole?**4 ? 1/4 1/4 1/4 1/4 1÷4 = 1/4 1÷ ¼ = 4 By Monica Yuskaitis**4**1= 4/4 1/4 1/4 1/4 1/4 1÷4 = 1/4 1÷ ¼ = 4 By Monica Yuskaitis**How many quarters are in a half?**1/4 2 1/4 ½ ÷1/4 = 2 Or: 2 quarters equals ½ dollar. By Monica Yuskaitis**Equivalent Fractions**• Name the same amount but have different numerators and denominators. • Or: Half a dollar = 2 quarters. 1 2 1 1 = 4 2 4 2 1 4 By Monica Yuskaitis**Equivalent Fraction Models**¼=2/8 1/8 1/8 1/4 1/4 1/8 1/8 1/8 1/4 1/8 1/4 1/8 So if you have 3 times as much, you have… 3 6 = 4 8 By M.Yuskaitis**To Find Equivalent Fractions**• Multiply the numerator and the denominator by the same number. • Or… 1 3 3 x = 3 3 9 By Monica Yuskaitis**To Find Equivalent Fractions**• Divide the numerator and the denominator by the same number. 4 4 1 ÷ = 12 4 3 By Monica Yuskaitis**Adding Like Denominators**Only add the numerators 1/4 1/4 3 1 4 + = 4 4 4 1/4 1/4 By Monica Yuskaitis**Subtracting Like Denominators**Only subtract the numerators 1/4 1/4 4 1 3 - = 4 4 4 1/4 1/4 By Monica Yuskaitis**To Add or Subtract Fractions with Unlike Denominators:**• 1/3 + 1/6 = ? • 1/3 + 1/9 = ? • Rewrite each fraction using the least common multiple.**Common Multiple**• A number that is a multiple of two or more numbers. Some multiples of 3 & 6 6, 12, 18, 24, 30, 36, 42 By Monica Yuskaitis**Shortcut for Finding the Least Common Denominator or Least**Common Multiple Check to see if the smaller denominator divides evenly into the larger denominator. 1 3 1 3 will divide evenly into 9, so 9 is your LCD or LCM. + 9 By Monica Yuskaitis**To Add or Subtract Fractions With Unlike Denominators**• Rewrite the fractions using the least common denominator or least common multiple. 1 = 5 1 = + 10 By Monica Yuskaitis**To Add or Subtract Fractions With Unlike Denominators**• Now just add the numerators. 1 x 2 = 5 10 x 2 = Remember when adding fractions you never add the denominators. 1 1 + 10 10 10 By Monica Yuskaitis**Subtract these Fractions**Use the short cut to find the Least Common Denominator (LCD). 1 2 1 - 8 By Monica Yuskaitis**Mixed Numbers**• Mixed numbers are whole numbers and fractions together. 1 3 1 1 1 = ½ 2 By Monica Yuskaitis**Shortcut for Finding the Least Common Denominator**Check to see if the smaller denominator divides evenly into the larger denominator. If it does, use the larger denominator for your LCD. By Monica Yuskaitis**Shortcut for Finding the Least Common Denominator**2 will divide evenly into 8, so 8 is your LCD or LCM. 1 3 2 1 1 + 8 By Monica Yuskaitis**To Add Mixed Numbers With Unlike Denominators**• Find the multiples of each denominator. 1 3 4 = 4, 8, 12, 16, 20, 30 1 1 + 10 = 10, 20, 30, 40, 50 By Monica Yuskaitis**Compare the lists of multiples. Circle the common**multiples between the two lists. 1 3 4 = 4, 8, 12, 16, 20, 24 1 1 + = 10, 20, 30, 40, 50 10 By Monica Yuskaitis**Find the equivalent fractions for 1/4 & 1/10 with 20 as**the denominator. Ask yourself what you multiply 4 by to get 20. 1 3 4 20 x 5 = 1 1 + 10 20 By Monica Yuskaitis**To Subtract Two Mixed Numbers with Unlike Denominators**• Borrow 1 whole. Rename. Add to what you already had, then subtract. 2 answer= 1 / 1 5 20 25 = = + 20 20 20 4 - 8 1 8 4 = 20 10 20 17 20**Try it!**1 3 - 1 • Answer= ? 2 3 5**Answer= 1 9/10**How did you do?**When would you multiply a fraction by a fraction?**• Your family eats 1/8 of 1/2 of a left-over wedding cake. 1/8 of 1/2 or 1/8 x 1/2 By Monica Yuskaitis**Jose had already read 1/2 of his novel. Today he read 1/12**of the 1/2 left. How much of the book has he read? 1/12 of 1/2= 1/24 or 1/12 x 1/2 = 1/24 By Monica Yuskaitis**Multiplying Fractions**• When you multiply two fractions that are between 0 and 1 the product is smaller than both fractions. By Monica Yuskaitis**Multiplying Fractions**½ x ¾ = 3/8 Look at the diagram on the next slide to understand why. By Monica Yuskaitis**Multiplying Fractions**½ x ¾ = 3/8 ½ of ¼ = 1/8 ¼ ¼ ¼ ¼ 1/8 1/8 1/8 By Monica Yuskaitis**How to Find a Fraction of a Fraction:**• When you see a fraction problem with the word “of”, multiply. 1 4 x of 2 9 By Monica Yuskaitis**Multiply your numerators straight across.**1 x 4 4 = 2 9 By Monica Yuskaitis**Then multiply your denominators straight across.**1 x 4 4 = 2 9 18 By Monica Yuskaitis**Simplify your answer. In this case we reduce.**1 x 4 4 2 2 ÷ = = 2 9 18 2 9 ÷ By Monica Yuskaitis**When would you multiply a fraction and a whole number?**• You walk a 4 mile route halfway. ½ of 4 or ½ x 4 • You walk a ¾ mile route twice. 2 x ¾ By Monica Yuskaitis**A $12 ticket to the magic show is on sale for 2/3 of the**original price. 2/3 of $12 or 2/3 x 12 By Monica Yuskaitis**How to Find the Fraction of a Whole Number**• The first thing to remember is “of” means multiply in mathematics. of = X (times) By M. Yuskaitis**Multiply.**1 x of 46 2 By Monica Yuskaitis**Change your whole number to a fraction by adding a one**underneath. 1 x 46 2 1 By Monica Yuskaitis**Multiply your numerators straight across.**1 x 46 46 = 2 1 By Monica Yuskaitis**Multiply your denominators straight across.**1 x 46 46 = 2 1 2 By Monica Yuskaitis**Simplify your answer. In this case we change an improper**fraction to a mixed number or a whole number. 23 1 x 46 46 2) = 46 2 1 2 By Monica Yuskaitis**Cross Simplifying:**• Sometimes you can cross simplify before you multiply instead of afterwards.**Cross Simplifying:**46 1 = X 1 2 23 1 X 46 46÷2= 23 = 1 2 X 1 2÷2 = 1