Transcript 12 - NCETM

Mathematics
Fractions Re-cap1
Equivalent fractions spider diagram
Cancelling fractions to their lowest terms
A fraction is said to be expressed in its lowest terms if the
numerator and the denominator have no common factors.
Which of these fractions are expressed in their lowest terms?
14
16
7
8
20
27
3
13
15
21
5
7
14
35
2
5
32
15
Fractions which are not shown in their lowest terms can be
simplified by cancelling.
Mixed numbers and improper fractions
When the numerator of a fraction is larger than the
denominator it is called an improper fraction.
For example,
15
is an improper fraction.
4
We can write improper fractions as mixed numbers.
15
4
can be shown as
15
=
4
3
3
4
Improper fraction to mixed numbers
37
Convert
to a mixed number.
8
37
8
8
8
8
+
+
+
=
8
8
8
8
8
+
1+1+1+1+
5
= 4
8
=
37 ÷ 8 = 4 remainder 5
5
8
5
8
37
=
8
This number is the remainder.
4
5
8
This is the number of times 8 divides into 37.
Mixed numbers to improper fractions
2
to an improper fraction.
7
3
2
37 =1 + 1 + 1 +
Convert
2
7
7
7
7
2
=
+
+
+
7
7
7
7
23
=
7
To do this in one step,
… and add this number …
3
2
23
=
7
7
Multiply these numbers together …
… to get the numerator.
Find the missing number
Finding a fraction of an amount
2
What is
of £18?
3
We can see this in a diagram:
2
of £18 = £18 ÷ 3 × 2 = £12
3
Finding a fraction of an amount
What is
2
of 3.5m?
5
1
To find 1 25 of an amount we need to add 1 times the
amount to two fifths of the amount.
1 × 3.5 m = 3.5 m
so,
1
and
2
of 3.5 m = 1.4 m
5
2
of 3.5 m = 3.5 m + 1.4 m = 4.9 m
5
7
We could also multiply by
5
MathsBlox
Using equivalent fractions
3
5
Which is bigger
or
?
8
12
To compare two fractions convert them to equivalent
fractions.
First we need to find the lowest common multiple of 8 and 12.
The lowest common multiple of 8 and 12 is 24.
3
5
Now, write
and
as equivalent fractions over 24.
8
12
×3
3
8
9
=
24
×3
×2
and
5
10
=
12
24
×2
so,
3
8
<
5
12
Ordering fractions