MATHEMATICSMultiplying with Fractions

Lesson Objectives

•The aim of this powerpoint is to help you…

• to multiply fractions by whole numbers

• to multiply fractions by fractions

Multiplying Fractions

• FIRSTLY convert any mixed numbers into improper fractions or write whole numbers over 1, then…

• Multiply the top numbers together

• Multiply the bottom numbers together

• Cancel down (if possible) and/or convert your improper fraction back into a mixed number

Example 1What are 5 lots of 3/10?

3 10

If you need to simplify your answer…

15 3 110 2 2

× = =

÷5

÷5

5×3 151×10 105 = ×

5 31 10

1

Example 2What is the product of 3/5 and 2/9?

3 2 5 9

If you need to simplify your answer…

6 245 15

× = =

÷3

÷3

3×2 65×9 45

Of…

• The word ‘of’ in mathematics implies ‘multiply’

• Therefore 3/5 of 2/9 means 3/5 × 2/9 (we did this in example 2)

• We can represent this pictorially…• Draw a rectangle.• Split it into 9 columns and shade 2 of them in yellow (this is the

2/9)

• Split it into 5 rows and shade 3 of them in blue (this is the 3/5)

• The overlapping ‘green’ section is 3/5 of 2/9 = 6/45 or 2/15

Example 2 (pictorially)

2 9

of = =3×2 6 25×9 45 15

35 =

Quick Practice

A 2 3 D 7 4

7 5 8 5

B 1 3 E 8 3

4 8 15 4

C 10 3 F 2 15

11 20 5 22

Work out your answers before clicking on to the next slide.

×

××

×

××

Answers

A × =

B × =

C × =

D × =

E × =

F × =

635

332

or

or

or

or

What next?

• Print out the notes called Frac5. Read them and make sure you answer any questions

• Work through all of the MyMaths lesson called Multiplying Fractions found at:

• http://app.mymaths.co.uk/93-resource/multiplying-fractions

• If you need more practice, try the worksheet called

MFrac-S0.xlsx.

• Now move on to the Frac-6 powerpoint