1.2 Real numbers 5
The number one halfis equal to two quartersand can be added to one quarterto
give three quarters:
The value of a fraction like 1 2 2 is unchanged if the numerator and the denominator
are both multiplied by the same number:
and the general method of adding fractions is (a) find a common denominator for
the fractions to be added, (b) express all the fractions in terms of this common
denominator, (c) add.
(2) Add and.
A common denominator is 31 × 151 = 115. Then
(3) Add and.
A common denominator is 41 × 161 = 124 , but the lowest (smallest) common
denominator is 12:
0 Exercises 8–
EXAMPLE 1.4Multiplication of fractions
This can be interpreted as taking two thirds of 4 2 5 (or four fifths of 2 2 3).
0 Exercises 14–
2
3
4
5
24
35
8
15
×=
×
×
=
1
4
5
6
3
12
10
12
13
12
+=+=
5
6
1
4
2
3
4
5
25
35
34
35
10
15
12
15
10 12
15
22
15
+=
×
×
×
×
=+=
=
4
5
2
3
1
2
12
22
2
4
=
×
×
=
1
2
1
4
2
4
1
4
3
4
+=+=