Approximately how long is a double-stranded DNA molecule with a molecular weight of 3x10^9 g/mol? Assume the molecular weight of one nucleotide is 333 g/mol, and that there are 10 base pairs for each turn of the DNA helix equalling 3.4nm in length.

Let's begin by assessing the molecule. If we divide the molecular weight by two, that will give us the weight for one strand of the helix. Knowing that one nucleotide is 333 g/mol, then dividing the weight of one strand by 333 g/mol will yield the number of nucleotides comprising that strand.
We also know that every 10 nucleotides, the helix turns, measuring 3.4nm. Therefore, dividing the number of nucleotides in the strand by ten will reveal the number of helical turns, each being 3.4nm in length. Finally, multiplying the number of helical turns by 3.4nm will yield our answer.