<span>According to the World Wildlife Fund humans started using more of Earth's resources than can be replenished sometime during the 80s, around 1985.</span>
Avogadro's number tells us there are 6.022 x 1023 molecules of water per mole of water. So, next we calculate how many molecules there are in a drop of water, which we determined contains 0.002775 moles: molecules in a drop of water = (6.022 x 1023 molecules/mole) x
