Two torches run on identical batteries. In one week, one torch's battery died, the other is still…

Why

Ankit's explanation is a real possibility — batteries genuinely do vary in quality, and it's the most direct guess when two seemingly-identical things behave differently. But 'lasts longer' can come from several different places besides the battery itself. How often and how long each torch was actually switched on matters enormously — a torch used for ten minutes a day drains far slower than one left on for hours. The bulb itself can differ in how much current it draws. Loose contacts or a slightly bent spring inside one torch can waste current even while it's off. Any of these would produce the exact same result Ankit saw, with both batteries being genuinely identical. Test: swap the two batteries between the torches and see whether the 'better' battery still lasts longer in the OTHER torch — if it does, it really is the battery; if not, the torch itself was the difference. No, there could be other reasons: usage, the bulb, and the torch's own wiring can all explain the same outcome just as well as battery quality.