Download multiplication of fractions

Fractions
MULTIPLICATION OF FRACTIONS
Any fractions can be multipled.
The bottom numbers DO NOT have to be the same.
All you do is: multiply the top numbers and
multiply the bottom numbers.
Examples
(a)
3
4

1
5

3
20
(b)
4
5

3

4
5

12
5

22
5
(3 x 1)
(4 x 5)

3
1
(All whole numbers can be
written over 1.)
Check for cancelling whole numbers
Multiply these fractions and check the answers to
see if they can be simplified.
1)
2
1
x
3
5
4)
4
x2
3
2)
5
1
x
6
3
5)
4
2
x
10
5
3)
3
1
x
4
2
6)
3x
1
4
10
Fractions
All fractions can be multiplied like this but it is sometimes better to cancel
first if possible.
You can cancel any number on top with any number at the bottom.
You can cancel either up and down or diagonally.
Examples
1
(c)
OR
2
5
×
6
84
1
5
24
(1x5)
(6x4)
2
5
5
×
=
63
8
24
(1×5)
(3×8)
=
Cancel the 2 and the 8
by 2, giving 1 and 4.
Cancel the 2 and the 6
by 2, giving 1 and 3.
As long as a top number is always
cancelled with a bottom number, the
answer will be the same.
It is sometimes possible to cancel more than once.
(d)
7
82
×
13
(e) 1 5
1
×
8
41
Cancel the 12 and 8 by 4
.giving 3 and 2
Cancel the 3 and 15 by 3
.giving 1 and 5
12
7
=
15 5
10
×
13
Cancel the 5 and 15 by 5.
12
1
=
1531
8
Cancel the 4 and 12 by 4.
Cancel the 3 and 3 by 3.
2
Fractions
Cancel first if possible:
1)
3
2
x
7
5
6)
2
10
x
5
12
2)
4
5
x
5
9
7)
3
6
x
4
15
3)
2
6
x
3
10
8)
9
12
x
15
15
4)
7
x
10
5
9)
1
8
x
2
9
5)
6
1
8
x
10)
7
12
x
4
20
If multiplying mixed numbers, they need to be changed to top-heavy
fractions first.
The whole numbers CANNOT be kept separate.
Examples
(f)
4 51
=
=
=
7
21
51
7
1
7
×
×
2
1
3
1
5
31
Remember: 4 x 5 = 20
and 1 = 21
Cancel by 5
Cancel by 3
Multiply
Any number over 1 is a whole number
3
Fractions
(g)
1 21
×
=
3
21
×
=
45
4
=
11 41
×
3 34
2
×
1
15
4
2
1
Have a go at these:
1
1)
32
2)
1
3)
10
4)
43
5)
29
x
3
x
4
2
2
x
6
8
35
7)
46
25
8)
34
1
5
9)
1 10
10)
63
3
17
4
x 1
x
3
6)
4
45
1
3
7
2
1
x
72
x
2 10
x
29
x
5
x
35
1
2
3
Check your answers, then discuss with your tutor what you need to
work on next.
4
Fractions
Answers
(Page 1)
1)
2
15
4)
2
2)
5
18
4
5) 25
3)
3
8
6)
23
1
15
(Page 3)
1)
6
35
1
6) 3
2)
4
9
3
7) 10
3)
2
5
12
8) 25
4)
32
5)
3
4
1
4
9) 9
10)
1
1 20
5
Fractions
(Page 4)
5
1)
28
6)
27
2)
22
7)
84
3)
28
8)
83
4)
55
9)
82
5)
10 3
10)
24
1
3
2
3
1
1
6