The main scale of a vernier callipers has $n$ divisions/cm. $n$ divisions of the vernier scale coincide with $(\mathrm{n}-1)$ divisions of main scale. The least count of the vernier callipers is, (1) $\frac{1}{n(n+1)} \mathrm{cm}$ (2) $\frac{1}{(n+1)(n-1)} c m$ (3) $\frac{1}{n} \mathrm{~cm}$ (4) $\frac{1}{n^{2}} \mathrm{~cm}$