Can anypne help me? See the picture below

Question

kamille · Answer

attachment

kamille · Answer

@aaronq can you take a look again, please?

aaronq · Answer

you need to extrapolate (or interpolate, i forget which is which). 

basically, find 0.25 abs on the vertical axis and draw a straight line to intersect the graph, then draw a line down to the other axis to get the concentration. |dw:1389040883955:dw|

Next you need to find the original conc (i.e. before dilution)

kamille · Answer

now I get 125 µg/ml, but the answers I can choose from is

now I get the final concentration, but how to get the original one?

aaronq · Answer

think bout it, you didn't change the solute only the solvent, hence dilution. What formula do you use for dilutions?

kamille · Answer

v1c1=v2c2?

v1=10µl
v2=500µl
c2=125µg/ml

c1=v2*c2/10=6250µg/ml 

is this correct?

aaronq · Answer

yes

kamille · Answer

thank you:))

aaronq · Answer

no problem !