.
Ratio
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Ratio is a way of showing how something is SHARED out
The ratio of chocolate to
flour in my cake is 2:5
This Means for every 2 cups of chocolate
add 5 cups of flour
Skills:
Simplify a ratio (smallest whole numbers)
These ratios all simplify to the ratio 2:5
4:10 8:20 6:15 20:50 10:25 12:30
14:35
80:200
0.2:0.5
Hint: to simplify use the fraction function on the calculator (putting
smallest part of ratio on the top of fraction)
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Ratio A
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A Ratio compares the quantities or amounts (has the same units)
A Ratio is used to describe how something is shared between groups.
eg Ratio of Juice to water = 4:1
eg Ratio of Teachers to Students to Outdoor Instructors = 1:25:2
Bob has $1.20 and Betty has $3.80 They combine their money, buy a lotto ticket
and win $450. How could the money be shared fairly?
1) What is the ratio of Bob:Betty’s money they combined? =
2) Simplify this ratio =
3) What fraction of the ration is Bobs? =
4) Share the $450 by this ratio =
and Betty’s? =
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Ratio B
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SKILLS:
 Write information as a ratio (watch order of numbers)
 Simplify ratios (Must be same units & should be whole numbers)
eg 2.4kg:1000g = 2.4kg:1kg = 24kg:10kg = 12:5 ratio
 Splitting into a given ratio
eg split 85kg into the ratio 12:5
1) Find total of ratio parts
eg 12 + 5 = 17
2) Find the fraction for each part
eg
12 5
:
17 17
3) Find the amount for each part
eg
12
17
Or
1) Find total of ratio parts
eg 12 + 5 = 17
x 85kg = 60kg
5
17
x 85kg = 25kg
2) Divide the amount by this ‘total’ eg 85kg ÷ 17 = 5kg (each part is worth 5kg)
3) Multiply this by the ratio
eg 12 x 5kg = 60kg
5 x 5kg = 25kg
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Ratio C
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Simplify these ratios
1) 24:60 =
Gamma
Simplify p53 Ex 4.02
Share p57 Ex 4.03
2) 30%:60%:10% =
3) 4.8kg:3600g =
4)
1
3
:
4
5
5) A map scale is 1cm : 4km
A 8.5cm map line is ? km
6) Split 84 into the ratio 5:1
7) Share $460 into the ratio 2:1:4 (round sensibly)
8) If a fuel mix is a 53:2 ratio of petrol to oil.
If I have 1.6 litres of oil, how much fuel mix can I make?
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Ratio Example A
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Splitting up given a ratio
Example 1
Share an inheritance of $48 into the ratio 5:1
Steps
5 + 1 = 6 parts
$48 ÷ 6parts = $8
5:1
1) Add the ratio 'parts' together (how many 'parts'
total?)
2) What is 1 'part' worth?
3) Share the ratio
5 x $8 : 1 x $8
$40 : $8
Write the ratio in the correct order
(if 1:5 then $8:$40)
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Example 2
Ratio Example B
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Bob & Bill build a boat. Bob works for 12hr and Bill
works for 30hr
They sell the boat for $840.
If they share the money according to the time
worked, how much will each person get?
Steps
12 + 30 = 42 parts
1) Add the ratio 'parts' together (how many 'parts'
total?)
$840 ÷ 42parts =
$20
2) What is 1 'part' worth?
12:30
3) Share the ratio Bob:Bill
12 x $20 : 30 x $20
$240 : $600
Bob gets $240 and Bill gets $600