What will be the percentage error in measurement of time? [closed]

The least count of a stop watch is 0.2 s .The time of 20 oscillationsof a pendulum is measured to be 25.What will be the percentage error in measurement of time?

closed as off-topic by user191954, rob♦Nov 9 '18 at 18:14

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Total time measurement: $25s \pm 0.2s$
Error in one oscillation: $\frac{25s \pm 0.2s}{20} = 12.5s \pm 0.01s$
Hence Percentage error: $\frac{0.01s}{12.5s} \approx 8 \cdot 10^{-4}$
• If the divisions are every 0.2 seconds then any time between 24.9 and 25.1 seconds will be registered as 25.0 seconds so should it not be $25.0 \pm 0.1$ seconds? – Farcher Apr 14 '16 at 16:09