Chapter 2Fractions

2-1B: Estimating FractionsWhen do I Use….

•Compatible numbers – when you are estimating a fraction & a whole number.Ex: ¼ x 25 = ¼ x 24 = 6•0, ½, 1 – when you are estimating with 2 proper fractions.Ex: 5 3 1 1

6 8 2 2

•Whole numbers – when you are estimating mixed numbers.Ex: 5 ¼ x 6 ¾ = 5 x 7 = 35

= 1 x x =

2-1D Multiply fractions & Whole Numbers

• Write the Whole Number as a fraction by placing it over 1.

• If you can, cross cancel & then multiply the numerators and the denominators (key concept – p. 96)

8 x ¼ = 8 1 2

1 4 1x = or 2

1

2

1 10 2

5 11 11

10 4 10 10 1

12 1 12 3 3

=

x

2

1

4

x

x1

3

Multiply 2

Proper Fractio

ns

Multiply a

Proper Fraction

& Whole number

with a Mixed

Number answer.

= = = 3

Change the Improper fraction to a Mixed number

2 – 2 (B) Multiply Fractons

2-2 (C & D) Multiplying fractions and Mixed Numbers

Change the mixed numbers into Improper fractions

Check to see if you can cross cancel.Multiply and Simplify.If your answer is an Improper fraction you

will need to change it into a Mixed Number.

Ex: 2 5 8 5 20 2

3 6 3 6 9 9x x2 = = 2

4

3

2-3 (B – D) Dividing Fractions & Mixed Numbers

To DIVIDE fractions – flip the 2nd fraction and then multiply.

To DIVIDE Mixed Numbers you need to:a) change the Mixed Number to an Improper

fraction.b) flip the 2nd fraction.c) multiply. Ex: 5 15 17 16 136 1

6 16 6 15 45 45÷ = x =

3

8

= 32