metric and other measurments

Question

A lab technician is preparing agar medium. The medium requires 21grams of agar, 500mg of dextrose, 3dg of sodium, and 1cg of potassium per 1,000mL of distilled water.

 

 

B. If each culture dish uses 50 mL of the agar medium, what would the total weight in mg of dry ingredients be per culture dish?

Answer 1

First, for the 1,000 mL medium, convert all masses to mg.

 

agar         21 grams   = 21,000 mg      (1,000 mg = 1 gram)

dextrose   500 mg      =     500 mg

sodium         3 dg       =     300 mg      (100 mg = 1 dg)

potassium     1 cg       =       10 mg      ( 10  mg = 1 cg)

 

now, use the fraction of 50 mL / 1,000 mL  =  1/20   or  0.05 times all the above in mg. 

 

agar         = 21,000 * 0.05   = 1,050 grams

dextrose   =      500 * 0.05   =     25 grams

sodium     =      300 * 0.05   =     15 grams

potassium =       10 * 0.05   =     0.5 grams