mg to ml conversions

Question

If a drug has a concentration of 500 mg per 10 mL, how many milliliters are needed to deliver 7 grams of the drug?
Express your answer rounded to the nearest milliliter.

Answer 1

500 mg per 10 mL

500 mg is 0.5 g (to go from mg to g you move the decimal point 3 places to the left-500 is the same as 500.)

it takes 10 mL to deliver 0.5 g

it takes 20 mL to deliver 1 g

to deliver 7 g it takes 7*20=140 mL

you could also set up a proportion...

500 mg/10 mL=7000 g/ ? mL

7000/500=14 and 14*10=140, or...

0.5/10=7/n

0.5n=70

5n=700

n=140