If 15 drops of ethanol from a medicine dropper weigh 0.60g, how many drops does it takes from a dropper to dispense 0.1mL of ethanol? The density of ethanol is 0.80g/mL.
How many grams is 0.1 mL ethanol. That's mass = volume x density
mass = 0.1 mL x 0.80 g/mL = 0.08 g.
From the problem you know 15 drops = 0.60 g so
0.60 g/15 drops x #drops = 0.08
Solve for # drops = ?