Question

How do you convert 3.9 x 10^5 mg into decigrams?

Answer 1

The prefix `m` (milli) means `1/1000` or `10^-3`

Deci (prefix `d`) means `1/10` or `10^-1`

Explanation:

So `1000mg=1gand 10dg=1g->100mg=1dg`
The conversion factor is: divide by `100=10^2`

`(3.9*10^5)/10^2=3.9*10^(5-2)=3.9*10^3dg = 3900dg`

Btw:
`dg` is hardly ever used. `mg,g,kg` are the usual weight measures.
(and the metric ton for heavy stuff).