FV (future value), PV (present value), IY (interest rate), PMT (periodic payment) and N (number of periods) are all variables used in time value of money calculations. They are related to each other in the following ways:

1. FV and PV are inversely related - as one increases, the other decreases. This is because FV represents the future value of an investment, while PV represents its present value.

2. IY is the interest rate used in the calculation and affects both FV and PV. As IY increases, both FV and PV increase.

3. PMT is the periodic payment made towards an investment and affects the FV and PV calculations. If PMT is positive, it reduces the PV and increases the FV. If PMT is negative, it increases the PV and reduces the FV.

4. N is the number of periods over which the investment is made and affects both FV and PV. As N increases, FV increases and PV decreases.

In summary, FV, PV, IY, PMT and N are all interrelated variables that affect each other in time value of money calculations.