If 15 drops of ethanol from a medicine dropper weigh 0.60g, how many drops does it takes from a dropper to dispense 1.0ml of ethanol? density of ethanol is ethanol is 0.80g/ml.

20.0 drops.

Explanation:

Where, d is the density (d = 0.80 g/ml),

m is the mass (m = 0.60 g),

V is the volume (??? ml)

∴ V = m / d = (0.60 g) / (0.80 g/ml) = 0.75 ml.

Using cross multiplication:

15.0 drops will dispense → 0.75 ml of ethanol.

??? drops will dispense → 1.0 ml of ethanol.

∴ The number of drops that will dispense 1.0 ml of ethanol = (1.0 ml) (15.0 drops) / (0.75 ml) = 20.0 drops.