Multiplying with Fractions Mathematics Multiplying 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

5 1 Example 1 3 10 If you need to simplify your answer… 15 3 1 10 2 2 What are 5 lots of 3/10? 3 10 If you need to simplify your answer… 15 3 1 10 2 2 5 3 1 10 5×3 15 1×10 10 5 × = × = = ÷5   1

Example 2 What is the product of 3/5 and 2/9? 3 2 5 9 3 2 5 9 If you need to simplify your answer… 6 2 45 15 3×2 6 5×9 45 × = = ÷3 

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) 9 3 5 3×2 6 2 5×9 45 15 of = = =

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 D 7 8 × 4 5 = E 8 15 × 3 4 = F 2 5 × 15 22 = A 2 7 × 3 5 = B 2 5 × 4 15 = C 10 11 × 3 20 = 6 35 28 40 or 7 10 3 32 24 60 or 2 5 30 110 or 3 11 30 220 or 3 22

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