iOS calculator hidden backspace

True story: Just yesterday I was tapping away in the iOS calculator app, adding up a long list of expenses for my company's monthly P&L statement.

And because my fingers fly quickly, occasionally I'd hit the wrong number. Aaargh! Calculator lacks a backspace key, so my only option was to clear the entire entry and tap it out again. Right?

Nope. Turns out the app does have a backspace option -- one that's completely hidden and that you'd probably never find by accident.

The secret: Swipe either direction across the numbers. Not the keypad numbers, but the numbers up top, in the black.

Presto! One swipe removes the last number entered. Another swipe removes the next one. And so on.

OK, be honest: Did you already know this one? I didn't, and I've been an iOS user for a looong time.