mathematics express as fractions. lesson objectives the aim of this powerpoint is to help you… to...
TRANSCRIPT
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