Hello,
I have 38.8ug/ml (u = micrograms, don't know how to get the symbol) DNA in solution. Two questions: 1) If I add 1.4ul of this solution to 18.6ul of solution what is the formula to calculate the concentration of DNA in my new 20ul solution? 2) If I want 100ng of DNA in the new solution, how to calculate how much of the 38.8ug/ml DNA do I add, with a final volume of 20microliters?
Thank you for your help.

Volume1 x Concentration1 = Volume2 x Concentration2

V1 x C1 = V2 x C2

So Q1)

1.4ul X 38.8ug = (20ul) x ?

rearrange

remember in these kind of questions to make sure all the units are the same - not a problem but will be required for Q2.

It's the same equation for the second qustion as well.