Cambridge International Mathematics

Assumed Knowledge (Number) 9

Acommon fractionconsists of two whole numbers, a

numeratorand adenominator, separated by a bar symbol.

TYPES OF FRACTIONS

4

5 is aproper fraction fthe numerator is less than the denominatorg

7

6 is animproper fraction fthe numerator is greater than the denominatorg

234 is amixed number fthis really means 2+^34 g

1

2 ,

3

6 areequivalent fractions fboth fractions represent equivalent portionsg

LOWEST COMMON DENOMINATOR

Thelowest common denominator (LCD)of two or more numerical fractions is the lowest

common multiple of their denominators.

ADDITION AND SUBTRACTION

Toadd(orsubtract) two fractions we convert them to equivalent fractions with a

common denominator. We then add (or subtract) the new numerators.

Example 12 Self Tutor

Find:^34 +^56

3

4 +

5

6 fLCD=12g

=^34 ££^33 +^56 ££^22 fto achieve a common denominator of 12 g

= 129 +^1012

=^1912

=1 127

Example 13 Self Tutor

Find: 123 ¡ (^125)
123 ¡ (^125)
=^53 ¡^75 fwrite as improper fractionsg
=^53 ££^55 ¡^75 ££^33 fto achieve a common denominator of 15 g
=^2515 ¡^2115
= 154
D FRACTIONS
We can multiply both
the numerator and
denominator of a
fraction by the same
number to generate an
equivalent fraction.
4
5
numerator
denominator
bar (which also meansdivide)
IGCSE01
cyan magenta yellow black
(^05255075950525507595)
100 100
(^05255075950525507595)
100 100
Y:\HAESE\IGCSE01\IG01_AS\009IGCSE01_AS.CDR Wednesday, 10 September 2008 2:11:05 PM PETER
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