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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.

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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.

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

Earlier: All You Need Is a Dollar and a Train