it depends what kind flashlight you use, and the temperature has effection on it too.
duracell obv.
it take an duracell battery in a flashlight non-stop lasts exactly 15 hours
That's going to depend on how often, and for how long, the flashlight is turned on.
It's the other way around, the battery powers the flashlight. There's no set answer to that. It depends on the capacity of the battery and the power consumption of the flaslight.
duracell
Not if it's a regular duracell non rechargeable battery
there is alkaline in duracell and also zink
Duracell batteries are a brand of battery made by Duracell Inc. which is an American manufacturing company owned by Berkshire Hathaway.
Duracell
Duracell FTW
The battery ... without that it can't be a flashlight.
a Duracell size D