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Here are a few recommended readings before getting started with this lesson.
Paulina runs for two-sixths of her free time each day.
If Paulina has 5 hours of free time per day, how many hours does she run in 4 days? Give the exact answer.
The product of two fractions is equal to the product of the numerators divided by the product of the denominators. The resulting fraction is then simplified to its lowest terms, if possible.
a/b * c/d = a * c/b * d
Paulina drinks one-third of the water in her bottle before PE class. During class, she drinks ten-twelfths of the remaining water.
Notice that each third is divided into six smaller equal parts. The other third can also be divided into six parts. This will make it easier to find what fraction of the whole the red part represents.
The red part shows what fraction of the water bottle Paulina drinks during class.
10/12 * 2/3 Now compare each fraction with 12. These fractions do not have the same denominator. The denominators of the fractions are 12, 3, and 2. The least common denominator of these numbers is 12. Each fraction can be rewritten as an equivalent fraction with the common denominator to make it easier to compare them.
Rewrite | Compare with 12, or 612 | |
---|---|---|
10/12 | 10/12 | 10/12 > 6/12 |
2/3 | 2*4/3*4 = 8/12 | 8/12 > 6/12 |
Both fractions are greater than 12. An estimate for the product can then be 1 because the fractions can be rounded to 1. rccc Product: & 10/12 & * & 2/3 [0.5em] & ↓ & & ↓ Estimate: & 1 & * & 1 Since 1 is the identity element of multiplication, this product is also equal to 1. However, that does not say much about the original product, and 1 is not one of the possible answer options. Now think of rounding only one of the fractions to 1 one at a time.
Estimate for 1012* 23 | |
---|---|
Round 1012 to 1 | 1 * 2/3 = 2/3 |
Round 23 to 1 | 10/12 * 1 = 10/12 |
The fraction 1012 can be simplified to 56. The answer is either 23 or 56. The fractions in the options are in simplest form and 23 is among the options. Therefore, the answer is 23.
In addition to a number line, the product can also be represented by an area model. In this model, the denominators are used to divide a rectangular diagram into smaller parts. Consider modeling the following product. 10/12 * 2/3 The denominators are 12 and 3. The rectangle is then divided into 12 columns and 3 rows.
The numerators determine which parts will be shaded. Since 10 is the numerator of 1012, 10 of the 12 columns will be shaded. Similarly, 2 of the 3 rows will be shaded.
In this model, the overlapping region represents the product. For this example, the product is 2036= 59.
The product of two fractions is equal to the product of the numerators divided by the product of the denominators. Practice finding the product of fractions. Simplify the answer to its lowest terms.
When multiplying fractions by whole numbers or mixed numbers, both factors should be in the form of a proper fraction or an improper fraction.
Rewrite 9 as 9/1
a/b=.a /9./.b /9.
Simplify quotient
Rewrite 19 as 15+4
Write as a sum of fractions
Calculate quotient
Rewrite 1+4/15 as 1 415
Paulina's PE class lasts for 1 512 hours. The table shows what fraction of the class time is allocated for various activities.
Activity | Fraction |
---|---|
Warm-up | 1/5 |
Instruction | 1/2 |
Playing a game | 1/10 |
Cool-down | 1/5 |
Part of 1 512-hour Class | ||
---|---|---|
Activity | Fraction | |
Warm-up | 1/5 | |
Instruction | 1/2 | |
Playing game | 1/10 | |
Cool-down | 1/5 |
a bc=a* c+b/c
a * 1=a
Add terms
Rewrite 60 as 60/1
Multiply fractions
Multiply
Calculate quotient
Part of 1 512-hour Class | ||
---|---|---|
Activity | Fraction | |
Warm-up | 1/5 | |
Instruction | 1/2 | |
Playing game | 1/10 | |
Cool-down | 1/5 |
a*b/c= a* b/c
Multiply
Calculate quotient
Paulina loves a photo of her playing volleyball and prints it. The diagram shows the dimensions of the photograph.
The length of the photo is 8 34 inches and the width of the photo is 6 23 inches. Area = 8 34 * 6 23 Since the fractional parts of the mixed numbers are greater than 12, the mixed numbers can be rounded up. Area = & 8 34 * 6 23 & ↓ ↓ & 9 * 7 Therefore, the area of the photo is about 9* 7, or 63 square inches.
a bc=a* c+b/c
Multiply
Add terms
Multiply fractions
Multiply
a/b=.a /4./.b /4.
Calculate quotient
Rewrite 175 as 174+1
Write as a sum of fractions
Calculate quotient
Rewrite 58+1/3 as 58 13
a bc=a* c+b/c
Multiply
Add terms
a/b=a * 5/b * 5
a/b=a * 4/b * 4
a/b=a * 5/b * 5
a/b=a * 3/b * 3
Multiply
Add fractions
Add terms
Multiply fractions
Multiply
a/b=.a /6./.b /6.
Calculate quotient
Rewrite 3233 as 3200+33
Write as a sum of fractions
Calculate quotient
Rewrite 64+33/50 as 64 3350
To multiply a fraction by a whole number, the whole number is multiplied by the numerator of the fraction. To multiply mixed numbers, the mixed numbers can be converted into improper fractions before multiplying. Practice finding the product of fractions. Simplify the answer to its lowest terms.
The important point in multiplying fractions is to ensure that the fractions are either proper fractions or improper fractions. 1 26 * 2 = 8/6 * 2/1 The final step usually involves simplifying the resulting fraction. However, to make calculations easier, first check if the two fractions are already in their lowest forms. If not, the fractions can be simplified first before multiplying them. 4 & 8/6 &* 2/1 = 4/3 * 2/1 = 8/3 3 & Consider the challenge presented at the beginning of the lesson. Paulina devotes two-sixths of her free time to exercise.
Start by finding the number of hours Paulina spends running in a day.
Rewrite 20 as 18+2
Write as a sum of fractions
Calculate quotient
Rewrite 6+2/3 as 6 23