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Starter
If 4 oranges cost $3.60, how much
will nine oranges cost.
1 orange 90 cents
9 oranges $8.10
It takes 5 men 4 hours to chop up
some firewood. How long would it
take two men?
1 man 20 hours
2 men 10 hours
Starter
In a duck egg the ratio of yolk weight
to egg-white weight is 3:2. If the
egg-white weighs 14g, calculate the
weight of the yolk.
Yolk = 21g
The ratio of weight lifted to their
own body weight for a male Olympicclass weightlifter can sometimes
exceed 5:2. If a weightlifter weighs
80kg, what weight would he aim to
exceed?
Aim to lift 200kg
Note 9: Significant Figures
The number of significant figures a
number has, is the total number of
digits that represent it.
Example: 3147 (4 sf)
Zeros are significant when they are:
inbetween other numbers
both at the end of a number and
after the decimal point
Examples:
9.703
7.40
(4 sf)
(3 sf)
Zeros are not significant when they are:
at the front of a number
at the end of a number with no decimal
point
Examples: 0.036
24000
(2 sf)
(2 sf)
Note 10: Rounding
To round a number to a given number of
decimal places/significant figures:
 Underline the number of decimal
place/significant figures required
 Look at the next digit, if it is
 less than 5, drop all numbers not
underlined
 5 or more, then add one to the last
digit underlined and drop all other
numbers
 For significant figures, zeros may be
needed as place holders
Examples: 3.8194 (2 dp)
4368 (2 sf)
12.895 (2 dp)
0.0546 (1 sf)
(3.82)
(4400)
(12.90)
(0.05)
Note 11: Standard Form
Very large and very small numbers
are written in standard from.
Example: 3.14 × 102
Standard Form
Number
Move the decimal point to the right if
the power is positive and to the left if
the power is negative.
Examples: 5.364 × 102 536.4
2.46 × 10-1 0.246
Number
Standard Form
Move the decimal place to after the first
significant figure. Find the value of the
power.
Examples: 5812 5.812 × 103
1.9 × 10-2
0.019
Page 25
Exercise P
Page 27
Exercise R and S