MATHEMATICSExpress as Fractions

Lesson Objectives

•The aim of this powerpoint is to help you…

• to express one value as a fraction of another

Express as a Fraction

• To express one value as a fraction of another you must first ensure that BOTH values have the same type of units.

• If they don’t you will have to convert one of them.

• Once they both have the same type of units, write the first value over the second value.

• Make sure the fraction is valid (i.e. doesn’t contain fractions or decimals within the fraction) by finding an equivalent fraction

• If the question asks for the answer in its simplest terms remember to cancel the fraction down if possible.

Example 1

• Express 50p as a fraction of £2.

• First convert 50p into pounds OR convert £2 into pence….. (£2 = 200p)

• Now we have express 50p as a fraction of 200p 50200

÷50 1÷50 4≡

Example 2

• What fraction of 3kg is 1600g?

• First convert 1600g into kg OR convert 3kg into grams….. (3kg = 3000g)

• Now we need 1600g as a fraction of 3000g 1600 3000

÷200 8÷200 15≡

Example 3

• In a test of 20 questions, Cara got 13 questions correct. What fraction of the questions did she get wrong?

• Note: She got 20 – 13 = 7 wrong

• We have to express 7 as a fraction of 20 720

Quick Practice

For each of the following, express the first value as a

fraction of the second value, giving your answer in its

simplest terms.

A 20p, £5 D 34mm, 5cm

B 15cm, 1m E 30p, £1

C 16g, 80g F 1200m, 4km

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

Answers

A 20p, £5 20p, 500p

20

500

B 15cm, 1m 15cm, 100cm

15

100

C 16g, 80g

16

80

Both numbers end in 0 so divide them BOTH by 10

Both numbers are even so divide them BOTH by 2

Now both numbers are even so divide them BOTH by 2

Both numbers end in 5 and 0 so divide them BOTH by 5

= 1 25

= 320

= 840

= 1 25

= 420

= 210

= 1 5

You can divide by 2 several times!

Answers (cont’d)

D 34mm, 5cm 34mm, 50mm

34

50

E 30p, £1 30p, 100p

30

100

F 1200m, 4km 1200m, 4000m

1200

4000

Both numbers end in 00 so divide them BOTH by 100

Both numbers are even so divide them BOTH by 2

Both numbers end in 0 so divide them BOTH by 10=

310

=1240

= 17 25

= 310

Both numbers are in the 4x table so divide them BOTH by 4

What next?

• Print out the notes called Frac7. Read them and make sure you answer any questions

• If you need more practice, try the worksheet called

ExpFrac-S1.xlsx.

• Now move on to the Frac-8 powerpoint