Cambridge International Mathematics

Assumed Knowledge (Number) 21

1 Convert:

a 0 : 65 into an equivalent fraction, percentage and ratio

b 60% into an equivalent fraction, decimal and ratio

c 2:5into an equivalent fraction, decimal and percentage

d^58 into an equivalent decimal, ratio and percentage.

2 Copy and complete: Decimal Fraction Ratio Percentage

1

4

85%

0 : 36

4:5

0 : 2

5:4

200%

(^512)
You are expected to be able to round numbers to various levels of accuracy.
These include: ² to a certain number ofdecimal places
² to a certain number ofsignificant figures
² to thenearest integerorwhole number.
DECIMAL PLACE ROUNDING
In many situations we may be given a measurement as a
decimal number. Stating theexactvalue of the measurement
may not be particularly important; what we want is a good
approximationof the measurement.
For example, since 1924 the Olympic marathon has been
measured as exactly 42 : 195 km or 26 : 2187 miles. The
exact value is rarely quoted, however, since most people
use approximations; they commonly say 42 km, 42 : 2 km,
26 miles, or 26 : 2 miles.
RULES FOR ROUNDING
²
Look at thefirstdecimal place.
If the digit is 5 , 6 , 7 , 8 or 9 , roundup.
If the digit is 0 , 1 , 2 , 3 or 4 , rounddown.
H ROUNDING NUMBERS [1.11]
5 : 6
look at this
then round
Rounding to the nearest whole number
EXERCISE G
IGCSE01
cyan magenta yellow black
(^05255075950525507595)
100 100
(^05255075950525507595)
100 100
Y:\HAESE\IGCSE01\IG01_AS\021IGCSE01_AS.CDR Thursday, 11 September 2008 9:40:11 AM PETER
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