As you'll recall, the MTA's gratuitous, financially unsound, and arguably strike-encouraging holiday-season ride-for-a-buck special left some riders with odd balances remaining on their Metrocards. A cantankerous pal was left with a single buck; we with $13. At first, we didn't know it was possible to add non-round amounts to a 'Card, but you quickly disabused us of that notion. So we hightailed it to our local IND stop, at which we further proved our stupidity and, without going into an explanation, left the station with a balance of $33.40, which was far worse than the $13 we entered with.

We knew what we'd done, and we knew what we needed to do to fix it. (33.40 + 1.2x = y, solve for x so that y is an even number.) Before we could sit down for a few minutes with a pencil and calculator, however, the Comments and our inbox were flooded with the correct answers (thanks for that), along with a handful of incorrect answers (good effort, at least.) So how did things work out?

There seemed to us to be three choices.

Most simple would be to add $.60, which would easily bring us to an even $34. But if we did that, we'd be loosing the 20 percent bonus the MTA awards when you spend more than $10, and we do so hate to leave free money on the table. So the easy option, it seemed to us, was out of the question.

Next was to add $10.50. The bonus on that would be $2.10, and adding that $12.60 to our unfortunate $33.40 would leave us with an even $46. Problem solved.

But we also didn't really like leaving the station after all this effort without a perfectly round number on our card. (Have we mentioned we're a touch obsessive?) Playing around with the calculator a bit more, we found the perfect solution: If we were to add $13.83, we'd get a $2.77 bonus (assuming the Metrocard machine rounded as we'd expect it to), meaning $16.60 to our existing balance and leaving us with a perfect $50 on our Metrocard.

What to do? It was obvious.

From all this tumult, finally an ideal result, right? Wrong! The system would not allow an addition of $13.83. INVALID AMOUNT, we were told, which sort of hurt our feelings. Time for the fallback position.

Would it finally work?

It would. We were happy. Our commuting problems were solved.

And now, we beg you, let us never speak of this unpleasantness again.

Earlier:
All You Need Is a Dollar and a Train
A Gawker Investigation: Metrocards!