You can use the following Cost of Gas calculator to estimate how much you are spending on gasoline in an average month from this it will estimate your average cost of gas per year as well.
South Africa Population growth rate. Factbook > Countries > South Africa > Demographics. Population growth rate: 0.99% (2016 est.) Definition: The average annual percent change in the population, resulting from a surplus (or deficit) of births over deaths and the balance of migrants entering and leaving a country. The rate may be positive or negative.
The average population change is currently estimated at around 80 million per year. Annual growth rate reached its peak in the late 1960s, when it was at 2% and above. The rate of increase has therefore almost halved since its peak of 2.19 percent, which was reached in 1963.