Day 33 looks at Simple interest, Compound Growth and Decay. Here we take an in depth look at the formulae required to carry Simple interest problems first of all (IPRY) It is important that you convert the percentage to a decimal (rate). If you were to do this manually, find the percentage of the amount then multiply by the number of years.
The second half looks at Compound Growth and Decay. Here the rate is added/subtracted from one to create a multiplier and a version of the IPRY formula is used. Remember here, years is written as a power.