1. 13. Mathematics and communication
Study guide
13. Mathematics and communication

2. Mobile phone plans
The cost of making a mobile phone call is determined by the connection fee (or flagfall), call rate and the length of the call.
Call charge = Connection fee + Time used × Call rate.
Prepaid mobile phones require the user to purchase credit in advance.
Postpaid plans involve a contract that varies in length from one to two years. It involves a range of charges such as a connection fee, monthly access fees, call costs, disconnection fee and data charges.
HSC Hint – Remember to subtract the free calls from the call costs when calculating the monthly charge.

3. Phone usage tables and graphs
A step-function or step graph consists of horizontal line segments or intervals. The end points of the line segments consist of a closed circle or an open circle.
HSC Hint – The values on the vertical axis are read from the closed circle (shaded) and not the open circle.

4. File storage Files are used to store data in a storage device.
A bit is the smallest unit of data stored in an electronic device. A byte is a group of 8 bits.
To convert between file storage units use the calculator and the power of 2.
Unit
Symbol
Meaning
Exact value
Power of two
Byte B
One byte 1
(20)
Kilobyte KB
Thousand bytes
1024
(210)
Megabyte MB
Million bytes
(220)
Gigabyte GB
Billion bytes
(230)
Terabyte TB
Trillion bytes
(240)
HSC Hint – When converting to a larger unit multiply by the appropriate power of 2.

5. Digital downloads
The speed of data transfer is measured by the number of bits per second (bps) or the bit rate.
To convert data transfer rates learn the order of the prefixes.
Unit
Symbol
Approximate value
Bit per second
bps 1
Kilobit per second
Kbps
1000
Megabit per second
Mbps
Gigabit per second
Gbps
Terabit per second
Tbps
HSC Hint – An increase in the order of the prefix is a conversion factor of 1000.

6. Digital download statistics
People are downloading digital media at a great rate.
Use summary statistics (mean, median, mode, range and interquartile range) to interpret the effect of downloading music and video files.
HSC Hint – Mean, median and mode measure the centre of the data. Range and IQR measure the spread.