Which pair of quantities is worked out using the compound interest formula?

1. Inflation is the average increase in the price of goods each year, given as a percentage. 2. Because that increase applies again to the already raised price, the growth compounds. 3. Family trees grow the same way, since every person born can start another family. 4. Population growth and inflation are therefore both calculated using the compound interest formula. 5. Hire purchase instalments run on simple interest instead, so that option names the wrong formula. 6. A deposit is a once-off cash payment and grows at no rate at all, which rules it out too. _Source: Siyavula Mathematics Grade 10 (Everything Maths, CC BY 4.0), Chapter 9: Finance and growth_