\((\frac{1}{0.06} \div \frac{1}{0.042})^{-1}\)

= \((\frac{100}{6} \div \frac{1000}{42})^{-1}\)

= \((\frac{100}{6} \times \frac{42}{1000})^{-1}\)

= \((\frac{7}{10})^{-1}\)

= \(\frac{10}{7}\)

= 1.4285 \(\approxeq\) 1.43.