How had we never noticed the "Other Amounts" button before?

A friend emailed this morning expressing his frustration with finding a single dollar left on his Metrocard in wake of the MTA's ride-for-a-buck holiday-weekend promotion. ("What the hell am I supposed to do with one dollar," he bitched, "find a senior citizen to take for a ride?") We are slightly obsessive sorts, and accordingly we'd already worried about precisely this problem. So we posted his angry inquiry, and we awaited a flood of commiseration.

Instead we received a flood of contempt. It's an easy problem to solve, commenters told us — just add a buck, or 3 bucks, or so on, to a Metrocard, they said, and we'd be fine. But we sort of a remembered you could only add money in \$10 increments, and so we put on pants — and a raincoat — and we headed to the corner to check.

And we discovered we'd always been wrong. Yes, you can most easily add \$10 or \$20 or \$40, but there's also an option to add "Other Amounts," which would solve our friend's problem nicely — and our own, as we discovered we were carrying a \$13 balance.

Giddy with excitement, we set out to do just that. And that's when things got much, much worse.

Our first thought was to add \$7, to bring our Metrocard to an even \$20. But then we remembered that the 20 percent freebie only kicks in over \$10, and we didn't want to let that go to waste. If we added \$10 even, we'd be at \$25 with the bonus, which wouldn't solve our odd-number problem. So then the answer seemed obvious: Add \$17. We think we were distracted because we still weren't convinced this would work, like when you try to take \$25 out of ATM that lets you type in odd numbers, only to discover at last minute that your transaction won't complete. This time, it did.

And that's when we realized the true horror of what we'd done. We have no idea what we were thinking. We guess we somehow thought having a \$30 balance would yield us a full \$6 bonus, even though we'd actually paid only \$17. We were, of course, mistaken.

This fuckup is going to require a calculator to fix. And — even worse — algebra. What hath God wrought?