I feeling math retarded right now

[never_retreat]

If I have a digital clock that restarted when the power came back on reading 7 and its actually 3 how long has it been out?
The difference is 4 hours. So it was out for 8 correct?

[Jim147]

I was told there would be no math.

I have no idea how long the power was off but if your clock resets to 12:00 ( I have two that reset to 1:00) the power came back on seven hours ago.

[Fly320s]

If it is showing 7, it was probably reset 7 hours ago.

[lupinus]

Unless, of course, it's showing 7 pm. That'd be 19 hours ago. Or 7 am could have been 31 hours ago.

Or....

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[Doggy Daddy]

Is it a true digital clock, or is it one of those with the little plastic numbers on a wheel that flip over every minute? 

[grampster]

Who cares?

[Perd Hapley]

Is it a true digital clock, or is it one of those with the little plastic numbers on a wheel that flip over every minute? 

"I got you babe..."

[230RN]

It is an interesting math problem.  The hangup is there are too many whole-number sources of error.

I guess your clock either didn't have a backup battery, or it was dead.

I don't know if it could amount to a whole hour's difference on the display*, but many of those clocks had a backup battery (usually a 9UV) to keep the clock running during a power outage.  The battery usually ran a free-running oscillator divided down to approximately 60 Hz to keep the clock going.  (Most of them used the power line's 60 Hz as a time base, so a crystal-controlled oscillator wasn't necessary, but there were/are many variations on this theme.)

An old backup battery could have kept the clock running for a while, and then croaked.

Terry, 230RN

* I guess that's why Doggy Daddy asked about a flip-down display, since thumping on or dropping one of these clocks can result in the little tags flipping over anyhow.

[Doggy Daddy]

* I guess that's why Doggy Daddy asked about a flip-down display, since thumping on or dropping one of these clocks can result in the little tags flipping over anyhow.

Not quite.  It's because a mechanical "digital" clock wouldn't reset to zero (or midnight, or noon) when the power returned. It would just resume running from where it stopped.

[makattak]

The answer is we have absolutely no idea how long the power was out. All we can know is how long the clock has been on.

What we can say is that the clock has been on (likely) for 7 hours. (Or 19, or 31, or...) As it is now 3 o'clock, that means the clock came on at 8 o'clock.

That tells us nothing about how long the power was out without knowing when the power went out. You'd need to add an analog clock for that information.

[Scout26]

"I got you babe..."

Don't Drive Angry....