MathGrade 4 Mrs. Ennis Comparing Fractions Part 2 Lesson Twenty-One
7,777 + 333 = 8,080 – H = 7676 6 x Z – 4 = 38 40 x 8 = 9 x ___ = 54
6. At 3:00 the hands of the clock are perpendicular. Give another time when the hands are perpendicular. 7. Number of vertices o a cube?es in $1.65? Round to the nearest thousand: 46,580
9. Joey got a new puppy that weighed 4 pounds. This was half the weight of his bowling ball. How much does his bowling ball weigh? 10. If Sam bought a turkey sandwich for $4.95 and a drink for $0.95, how much change would he get from a $10 bill?
Comparing Fractions with Unlike Denominators
Comparing Fractions • Make sure the denominators are the same. • Compare the numerators. • If the denominators are not the same, then rewrite the fractions using a common denominator. • The new fractions should be equivalent to the original fractions.
Writing Equivalent Fractions • One way to find a common denominator is to multiply the two original denominators. 5 3 > 6 x 4 = 24 6 4 20 18 x 4 20 > 18 x 6 24 24
Writing Equivalent Fractions • One way to find a common denominator is to multiply the two original denominators. 3 6 < 5 x 9 = 45 5 9 27 30 x 9 27 < 30 x 5 45 45
Writing Equivalent Fractions • One way to find a common denominator is to multiply the two original denominators. 4 5 > 5 x 7 = 35 5 7 28 25 x 7 28 > 25 x 5 35 35
Another way to compare fractions is to find the least common multiple(LCM) of both denominators. • Use the LCM as the new denominator in the equivalent fractions. 7 5 < 9, 18, 27, 36, 45 9 12 12, 24, 36, 48, 60 20 < 21 x 3 x 4 20 21 36 36
Least Common Multiple (LCM) 6 4 > 5 8 32 > 30 x 5 x 8 32 30 40 40 5, 10, 15, 20, 25, 30, 35, 40 LCM = 40 8, 16, 24, 32, 40
Least Common Multiple (LCM) 4 2 < 6 10 10 < 12 x 3 x 5 10 12 30 30 6, 12, 18, 24, 30 LCM = 30 10, 20, 30,
Ordering Fractions • Find the LCM of the denominators. • Use the LCM to write equivalent fractions. • Put the fractions in order using the numerators.
Example - Order from Least to Greatest: 3 2 1 5 8 4 x 5 x 8 x 10 15 16 10 40 40 40 8, 16, 24, 32, 40, 48 1/4 < 3/8 < 2/5 5, 10, 15, 20, 25, 30, 35, 40 4, 8, 12, 16, 20, 24, 28, 32, 36, 40
Example - Order from Least to Greatest: 3 2 5 3 4 12 x 3 x 4 x 1 9 8 5 12 12 12 4, 8, 12,16, 20, 32, 3, 6, 9, 12, 15, 5/12 < 2/3 < 3/4 12, 24
Example - Order from Least to Greatest: 3 2 2 6 4 3 x 3 x 2 x 4 9 4 8 12 12 12 4, 8, 12,16, 20, 32, 6, 12, 18, 2/6 < 2/3 < 3/4 3, 6, 9, 12, 15
Let’s Try Some!
3 3 7 4 > = 9 5 7 20 5 2 4 2 < 8 10 5 6 <
4 5 3 6 < < 9 7 10 12 4 1 6 4 = 9 8 4 6 >
Order from Least to Greatest 7 1 1 4 10 4 4 5 4 7 5 10
Order from Greatest to Least 3 3 3 3 12 4 4 12 4 4 8 8
Order from Greatest to Least 5 2 2 14 9 3 3 27 14 5 27 9
Online Practice Video: Review Ordering Fractions Flash Cards
Math Fun: The Post Office has rectangular stamps for sale. How many different ways could the four stamps be arranged so that you buy them all attached? Here is one example. How many ways could five stamps be arranged so that you could buy them all attached?
Answer: 4 stamps -5 ways 5 stamps - 12 ways
Resources: • http://mathlearnnc.sharpschool.com/UserFiles/Servers/Server_4507209/File/Instructional%20Resources/G4WW1-4.pdf • http://www.mrhammond.org/math/mathlessons/ • http://www.ixl.com/math/grade-4/order-fractions-from-least-to-greatest • http://www.mathplayground.com/howto_comparefractions.html
