How can I convert SI units using a proportion?

Question

My Science teacher will only give me full credit if I use a proportion to convert the units. If you can please show me mathematically or explain in detail, I would greatly appreciate it.

ex. 75,056 ng to kg

Answer 1

Are you sure that's supposed to be nanograms?

k = 10^(-12) n

Answer 2

First a ratio, then a proportion.

The ratio is 1 kg/10^12 ng

  Then let X be your answer in kg.

    Then  1/10^12 = X/75056

      and......X = 75056 x 10^-12 or 7.5056x10-8 kg