Transcript KS4_RATIO_sharing[1] - gcse-maths

Share a quantity into a ratio
The task of sharing into a
ratio is a favourite question
on the SAT and GCSE
papers. A question, for
example, might ask you to
share 32 into the ratio 3 : 5
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Share 32 into the ratio 3 :
the three steps to follow are:
5,
ADD the ratio 3 + 5 = 8
To do this type
DIVIDE
answer
of this
problem,
youinto the
quantityfollow
to be these
shared 32 ÷ 8 = 4
three steps
MULTIPLY the ratio numbers by
this answer
3x4:5x4
12 : 20
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+
÷
x
Share these
into the given
ratio
Ratio
2:3
2:5
3:7
4:5
1:2:5
+
÷
Quantity
50
28
20
360
32
x
Share
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Share these into the given ratio
Ratio
2:3
2:5
3:7
4:5
1:2:5
Quantity
50
28
20
360
32
Share
20 : 30
8 : 20
6 : 14
160 : 200
4 : 8 : 20
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Finding an unknown number in a ratio
Example – If the ratio of red
beads black beads is 3 : 5, how
many black beads will I need for 21
red beads?
Red : Black
3:5
21 : ?
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Find the
number
that you
multiply 3
by to get
21.
(21 ÷ 3 = 7)
3 x 7 = 21
Red : Black
x 7
3:5
21 :35
x7
Multiply 5 by 7 to find
the missing number
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Find the missing numbers for these
ratios:
2 :
8 :
5
3 : 20
12 :
5 :
30 :
7 :
21 :
6
5
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Answers in RED
2 : 5
8 : 20
3 : 20
12 : 80
5 : 6
30 : 36
7 : 5
21 : 15
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Ratio – A Problem
9 April, 2016
Here are a questions that show the two
different types of ratio problem:
Fruity Mix is made from concentrated fruit
juices and water. The ingredients are apricot
juice, apple juice, pineapple juice and water in
the ratio 2 : 3 : 7 : 28.
a)How much of each ingredient is used to make
240 litres of Fruity Mix?
b)If 24 litres of apple juice are used, how much
of the other ingredients are needed?
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Fruity Mix is made from concentrated fruit juices and water.
The ingredients are apricot juice, apple juice, pineapple juice
and water in the ratio 2 : 3 : 7 : 28.
a) How much of each ingredient is used to
make 240 litres of Fruity Mix?
Add the ratio 2 + 3 + 7 + 28 = 40
Divide into the quantity 240 ÷ 40 = 6
Multiply the ratio:
2x6:
3x6 :7x6
: 28 x 6
12 litres : 18 litres : 42 litres : 168 litres
Apricot : Apple : Pineapple : Water
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Fruity Mix is made from concentrated fruit juices and water. The
ingredients are apricot juice, apple juice, pineapple juice and
water in the ratio 2 : 3 : 7 : 28.
b) If 24 litres of apple juice are used, how much
of the other ingredients are needed?
Apricot : Apple : Pineapple : Water
2
:
3
:
7
: 28
16
:
24 :
56
: 224
24 ÷ 3 = 8 so 3 x 8 = 24 You multiply all
the numbers by 8