fractions and decimals

Fractions and Decimals

Lesson 5-5 (Glencoe)

Unit 1: Comparing and Ordering Positive Rational Numbers and Integers (Cscope)

TEKS 7.1 B

7.1 Students represent and use numbers in a variety of equivalent forms. (B) convert between fractions, decimals. Whole numbers, and percents mentally, on paper, or with a calculator

Writing Fractions as Decimals The table shows the heights of the ten tallest buildings in Dallas.

BuildingHeight

(ft)

Bank of America Plaza 921

Renaissance Tower 886

Bank One Center 787

JP Morgan Chase Tower 738

Fountain Place 721

Trammell Crow Center 686

1700 Pacific Avenue 655

Thanksgiving Tower 645

Energy Plaza 629

Elm Place 625

• What fraction of he buildings are between 600 and 800 feet tall?

• Express this fraction using words and then a decimal.

810

• Express this fraction using words and then a decimal.

810

When the denominator of a fraction is a power of 10, use place value to write the fraction as a decimal

Words

eight tenths

Model Fraction

8/10

Decimal

0.8

Now you try…

What fraction of buildings are between 710 and 850 feet tall?

Express this fraction using words and then as a decimal.

BuildingHeight

(ft)

Bank of America Plaza 921

Renaissance Tower 886

Bank One Center 787

JP Morgan Chase Tower 738

Fountain Place 721

Trammell Crow Center 686

1700 Pacific Avenue 655

Thanksgiving Tower 645

Energy Plaza 629

Elm Place 625

What have we learned so far?

When a denominator of a fraction is a factor of 10, 100, 1000 you can use mental math.

Name some factors of:– 10– 100– 1000

Write each fraction or mixed number as a decimal.1) 7 THINK So,

Examples of using Mental Math:

20 7 20

35 100

x 5

x 5

7 20 = 0.35

2) 5 ¾ Think of the mixed number as a sum = 5 + ¾ You know ¾ = 0.75 so, = 5 + 0.75 Add mentally = 5.75 So, 5 ¾ = 5.75

Check Your Progress

a) 3/10

b) 3/25

c) 6 ½

= 0.3

= 0.12

= 6.5

Any fraction can be written as a decimal by dividing its numerator by its denominator. Division ends when the remainder is zero.

Write 3/8 as a decimal.– Denominator outside– Numerator inside the division icon

8 30.3

-240

Division ends when the remainder is zero

06

70 0

04- 5 6

0- 4 0

5

Check Your Progress

d) 7/8

e) 2 1/8

f) 2/3

g) 8 1/3

= 0.875

= 2.125

= 0.66

= 8.33

Putting it to Practice

Glencoe page 247 – 1-11 (odd and check your answers on pg. 296)– 13 - 43 (all)– 46 (if you cannot figure out the answer, write down

your thoughts)