\(7.5\times 10^{-4}\)
\(7.5\times 10^{-3}\)
\(7.5\times 10^{-2}\)
\(7.5\times 10^{-1}\)
Correct answer is B
\((0.3\times 10^{5})\div (0.4\times 10^{7})\\
\frac{3}{10}\times 10^{5}\div \frac{4}{10}\times 10^{7}=3\times 10^{4}\div 4\times 10^{6}\\
\frac{3\times 10^{4}}{4\times 10^{7}}=\frac{3}{4}\times 10^{-2}=0.75\times 10^{-2}\\
7.5\times 10^{-3}\)