A molecule is measured and the width is \( 3 \times 10^{-6} \mathrm{~cm} \). How long will a str of 225 similar molecules be? Give your answer in scientific notation.

To find the total length of 225 similar molecules, you simply multiply the width of one molecule by the number of molecules. The width of one molecule is \( 3 \times 10^{-6} \mathrm{~cm} \). Thus, the total length of 225 molecules is: \[ 225 \times (3 \times 10^{-6}) = 675 \times 10^{-6} \mathrm{~cm} \] Now, converting \( 675 \) into scientific notation gives us \( 6.75 \times 10^{2} \). Therefore: \[ 675 \times 10^{-6} = 6.75 \times 10^{-4} \mathrm{~cm} \] So, the length of a string of 225 similar molecules is \( 6.75 \times 10^{-4} \mathrm{~cm} \).