An introduction to Numbers Dr Andrew French
You will need to consult your times table and your tables of integer powers
You will find it very useful to learn the powers up to 16 3 = 4,096
The DECIMAL system is when numbers are written right to left in powers of ten. Only ten symbols are needed (0,1,2,3,4,5,6,7,8,9) plus a DECIMAL POINT to describe any number, of which there are infinitely many. Not bad eh? In ancient cultures a different symbol is used for each integer, just like the way we say ‘one’, ‘two’, ‘three’ etc. How are numbers ‘best’ written down? Does it matter? So means 1 x x x x x x
The decimal system enables us to perform arithmetic calculations on numbers (i.e. addition, subtraction, multiplication and division) in a straightforward, systematic way. You have been practising it for many years now! Note we can use the decimal system to help us work out multiplications using a small set of memorized results (i.e. your times table) 123 x 456 = = 40, ,088
Use the ‘matrix decimal expansion’ to work out (NO CALCULATOR!) 167 x 394 = 0.15 x 17.2 =
Use the ‘matrix decimal expansion’ to work out (NO CALCULATOR!) 167 x 394 = 0.15 x 17.2 = = 30,000 18, ,798 =
We don’t have to use the decimal system. In fact we can use any (integer!) number of symbols from two upwards. A two symbol (0 or 1) system is BINARY (which is used to store and manipulate numbers by computers) Binary numbers 0, 1 DecimalBinary x x x x x 2 0 = = Note = x x x x x x x x x x x What are the decimal integers (a) 64 (b) 73 in binary?
Binary numbers 0, 1 DecimalBinary x x x x x 2 0 = = Note = x x x x x x x x x x x What are the decimal integers (a) 64 is since 2 6 = 64 (b) 73 is since = 73 in binary? 1 x x x x x x x We don’t have to use the decimal system. In fact we can use any (integer!) number of symbols from two upwards. A two symbol (0 or 1) system is BINARY (which is used to store and manipulate numbers by computers)
Hexadecimal numbers 0,1,2,3,4,5,6,7,8,9,A,B,C,D,E,F DecimalHexadecimal x x 16 0 = = D2 4 x x x 16 0 = 4 x x = ABCDEF A sixteen symbol system is HEXADECIMAL, which is typically used to describe computer memory addresses. Decimal Hexadecimal or ‘base 16’ What is (a) 31 (b) 117 in hexadecimal?
Hexadecimal numbers 0,1,2,3,4,5,6,7,8,9,A,B,C,D,E,F DecimalHexadecimal x x 16 0 = = D2 4 x x x 16 0 = 4 x x = ABCDEF A sixteen symbol system is HEXADECIMAL, which is typically used to describe computer memory addresses. Decimal Hexadecimal or ‘base 16’ What is (a) 31is 1F since 1 x x 16 0 = 31 (b) 117 is 75 since 7 x x 16 0 = = 117 in hexadecimal?
Other ‘popular’ bases are: 12Duodecimal0,1,2,3,4,5,6,7,8,9,A,B 60SexagesimalUsed by the ancient Babylonians around 3000BC Note this wasn’t a proper ‘place value’ system as there was no zero! cuneiform digits Although it did appear later as