Uncertainty in position of an electron (mass = 9.1 x 10^-28 g) moving with a velocity of 3 x 10⁴ cm/s accurate upto 0.001% will be (use h/4$\mathrm{\pi }$ in uncertainty expression where h = 6.626 xl0^-27 erg-second).

Given mass of an electron(m) = 9.1 x l0-28 g' 
Velocity of electron (v) = 3 x lO⁴cm/s;
Accuracy in velocity = 0.00l% = $\frac{0.001}{100}$;
Actual velocity of the electron
$\left(\mathrm{\Delta v}\right)=3\times {10}^4\times \frac{0.001}{100}=0.3\mathrm{cm}/\mathrm{s}$
Planck's constant (h) = 6.626x10^-27 erg-sec.
$\therefore$ Uncertainty in the position of the electron
$\begin{array}{l}\left(\mathrm{\Delta x}\right)=\frac{\mathrm{h}}{4\mathrm{\pi m\Delta v}}=\frac{6.626\times {10}^{-27}\times 7}{4\times 22\times \left(9.1\times {10}^{-28}\right)\times 0.3}\\ =1.93\mathrm{cm}\end{array}$