-- problem: convert 7.23 cm to nm

-- go through the base unit (m)

-- centimeter = 10^-2 m

-- nanometer = 10^-9 m

     7.23 cm x (10^-2 m / 1 cm) x (1 nm / 10^-9 m)

-- cm cancels out

     7.23 cm x (10^-2 m / 1 cm) x (1 nm / 10^-9 m)

-- m cancels out

     7.23 cm x (10^-2 m / 1 cm) x (1 nm / 10^-9 m)

-- subtract exponents

     9 - 2 = 7

     7.23 x 10^-7 nm

I lost it when he started speaking to the woman.