9.1- Introduction
The Metric system
The metric system has almost universally been adopted as it is much easier to calculate accurately as all metric measurements are based on units of 10.
Milli – means one thousandth (or 1/1000)
Centi means one hundredth (or 1/100)
Kilo means one thousand (1,000)
Metric Measurements
Length is typically measured in:
Centimetre (cm) = 10 mm
Metre (m) = 100 cm
Kilometre (km) = 1,000m
Mass is measured in:
Kilogram (kg) = 1,000 grams
Tonne = 1,000kg
Volume is measured in:
Litre = 1,000ml
1,000 litres = 1m³

9.2- Estimation and Approximation
Decimal Places
To do this simply count the number of decimal places required (in the examples below its 2). Then look at the next digit along. If it’s 4 or less then just write in the number with the correct amount of decimal places. If the last decimal to round is 5 or above, write in the number with the last decimal place up by 1.

For example 1.3721 – becomes 1.37 (as the following 2 is less than 5).
Significant Figures
Significant figures involve using all the digits specified not just the decimal places.

9.3- Calculator Methods
Standard Form
Standard form is a way of writing down very large or very small numbers easily. 10³ = 1000, so 4 × 10³= 4000 . So 4000 can be written as 4 × 10³ . This idea can be used to write even larger numbers down easily in standard form.

9.4- Measures and Accuracy
Any measurement we make is rounded to some degree of accuracy or other to the nearest metre or to the nearest litre. The degree of rounding gives the possible values of the measurement before rounding.

When we calculate an area or a volume, the errors in the measurements will give an even larger error.

9.5- Summary and Review

9.6- Assessment 9
Question 1 : The number p written in standard form is 8 × 10⁵
The number q written in standard form is 5 × 10^-2
Calculate p × q and  \(\frac{p}{q}\) ? Give your answer in standard form.