laboratory math conversions?

Question

I do NOT understand this stuff!!

I can draw out the conversion tables, but it's figuring out WHAT to START with that I'm having a problem with.

For example:
A serum BUN reactivity was very high and required a dilution to complete the assay. If 100 microliters of serum was added to 0.5mL of dilutent but this was not adequate, so 200 microliters of the prior solution was added to 0.2mL of dilutent for the final assay. What is the dilution ratio of each dilution and the final dilution ratio?

Ugh...if I could just understand the language of what they are asking, I could figure this out. What are they asking me to do?

Answer 1

Try this
Break it down into steps.
Change to same measurements ie micro litres to millilitres.
1000 micro to 1 milli. so 100 micro/ 1000 = 0.1milli
First mixture is in the ratio of .1ml of serum to 0.5ml of dilutant
ie 1 of serum to 5 dilutant (both sides x 10)
ie a ratio of 1:5

if you take 0.2ml and add 0.2ml of dilutant this would be the
sames as 1 ml 1ml (both sides x 5)
same as taking 1 ml (of 1:5 solution) and adding 1 more dilutant ie a ratio of 1:(5+1) or 1:6 serum to dilutant.

You may want to turn it round to the traditional "x:1"

eg 1:5 divide both sides by 5 to make the rh side = 1
ie 0.2:1