2. Salma puts $1 000 into the bank. The bank pays 10% interest per year. How long is it before Salma has $1 500 in her account?

3. And in order to plot the graph, we needed points (from some simple calculations) After 1 full year, she has $1000 x 1.1 or $1100 After 2 full years, she has $1000 x (1.1) 2 or $1210 After 3 full years, she has $1000 x (1.1) 3 or $1331 and so on …

4. Time (in full years)Amount of money ($) 01000 11100 21210 31331 41464.10 51610.51 61771.56

5. The red curve shows the growth of the money in the account We now need to find when the y-coordinate reaches 1500 (hence the blue line)

6. Geogebra will give the coordinates of the point of intersection (point A on the diagram) The answer is – Salma will have $1500 after 4.254 years.

7. The growth of Salma’s money is described by the equation: A = 1000 x (1.1) t And we simply want to solve the equation 1500 = 1000 x (1.1) t This simplifies to 1.5 = (1.1) t Taking logs of both sides … log 10 1.5 = log 10 1.1 t ⇒ t = log 10 1.5 log 10 1.1 ⇒ t = 4.254 years ⇒ log 10 1.5 = tlog 10 1.1 (using one of our rules of logs)

8. To some degree the population is growing like Salma’s money Some questions … What’s the starting population? What is the percentage increase per year of the population?

9. http://www.worldometers.info/population/www.worldometers.info/population Or this ….