Calculator and TMV issues with required return

I occasionally make mistake with calculating required return because I put the wrong sign and get stupid score.

When we calculate required return, I put negative PV, positive FV, PMT is positive if expenses are greater than income, then goes N and I get the required return. This is fine. If I put

In 2015 AM (question 7) when you need to get how much must be PV after taxes, I have put in positive FV and PMT but the correct solution was negative PMT even though expenses were greater than income.

So my question is how do I figure it out. I got completely puzzled as I thought I got this silly thing in check. What confused me more, normally if you put in wrong sign you get the ERROR screen.

So the issue seems to be that I did not consider signs of PMT and FV. If these signs are opposite, PMT will be considered as inflow in terms of contribution by the investor. If the signs are the same then PMT would represent net expense.

what’s your conclusion on this one?

Signs don’t drive contributions/withdrawals its the other way round. If an investor keeps depositing funds into his account, it’s an outflow from the investors perspective and therefore PMT = -ve. If he keeps withdrawing, its an inflow for investor and PMT = +ve.