This is the formula used to calculate Simple Interest.
FV = P[1 + (r t)]
= P + P r t…………………………………………………………………………….Distribute P into the bracket [1 + rt]
The “1” come about when you factorise P + Prt = P (1 + rt)

P = Present Value (PV)
FV = Future Value or “amount”
r = Interest Rate
t = Time period (Years or quarters or months etc)