Gonna be easy

The period of oscillation of a simple pendulum is $$T=2\pi \sqrt{\frac{L}{g}}$$. Measured value of $$L$$ is $$20cm$$ known to $$1mm$$ accuracy and time for $$100$$ oscillation is found to be $$90s$$ using a wristwatch of $$1s$$ resolution. The accuracy in determination of $$g$$ is:

×