A vial contains radioactive iodine131 with an activity of 20
     A vial contains radioactive iodine-131 with an activity of 2.0 mCi/mL. If a thyroid test requires 3.0 mCi in an \"atomic cocktail.\" how many milliliters are used to prepare the iodine-131 solution?  1.5 times 10^-3 mL  1.5 mL  1.5 times 10^3 mL  6.0 times 10^-3 mL  6.0 mL  6.0 times 10^3 mL 
  
  Solution
Answer: 1.5 mL
Stock of I-131 activity = 2 mCi/mL
Required= 3 mCi
Cross multiplication.
2mCi------>1mL
3mCi------>= (3mCi x 1mL)/2mCi = 1.5 mL

