Question

A speck of dust is 1.2 x 10-6 m wide. Which of the following is the best wayto rewrite this quantity, using more appropriate units?A. 1.2 x 10-4 cmB. 1.2 x 10-9 kmC. 1.2 x 10-3 mmD. 1.2 x 10-6 mSUBMIT

Answer 1

The given quantity is

$1.2\ast10^{-6}m$

The general conversion rules are

$\begin{gathered} 1\operatorname{cm}=10\operatorname{mm} \\ 1m=100\operatorname{cm} \\ 1\operatorname{km}=100m \end{gathered}$$\begin{gathered} So \\ 1.2\ast10^{-6}m=1.2\ast10^{-6}\ast1m=1.2\ast10^{-6}\ast100\operatorname{cm} \\ =1.2\ast10^{-6}\ast100\ast10\operatorname{mm}=1.2\ast10^{-3}\operatorname{mm} \end{gathered}$

The answer is option c.