Transcript Sharing a quantity into a given ratio

Ratio
My bike’s fuel has
a ratio of
oil to petrol
1 : 25
Sounds
complicated
Using the simplest ratio to
describe different quantities.
Sue is explaining
how to use a ratio to
describe red and
green hearts.
Count the number of red and green hearts
4 RED and 8 GREEN
Record the numbers using headings like this
Red : Green
4:8
:
The
says ‘to’
Try to write the ratio in its
simplest terms
Red : Green
4:8
2:4
1:2
Divide ÷
by 2
The ratio of red to green is
Red : Green
1:2
This tells you that there
are 2 green hearts for
every red heart
Copy and complete this chart
Ratio
12 : 16
24 : 32
27 : 36
28 : 40
Simplest terms
Copy and complete this chart
Ratio
Simplest terms
12 : 16
3:4
3:4
3:4
7 : 10
24 : 32
27 : 36
28 : 40
Sharing a quantity into a given ratio
For example, share 36 into the ratio
2:7
First ADD the ratio 2 + 7 = 9
Second DIVIDE this answer into
the quantity to be shared 36 ÷ 9
=4
Third MULTIPLY the ratio by
this answer 2 X 4 : 7 X 4
This is the answer 8 : 28
To share into a given ratio, the things
to do are:
÷
+
X
Share 32 into the the ratio 3 : 5
3+5=8
32 ÷ 8 = 4
3 X 4 = 12 : 5 X 4 = 20
Answer 12 : 20
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
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
Finding an unknown number
that fits a given 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 : ?
First find the number that
you multiply 3 by to get 21
Red : Black
3:5
X7
21 : ?
Red : Black
3:5
X7
X7
21 : 42
Another Example
Red : Black
2:7
X6
12 : ?
2 X 6 is
12 so you
multiply
7 by 6 to
get the ?
Red :
Black
2: 7
X6
12 : 42
X6