The average annual precipitation worldwide must equal the quantity of water that

..has evaporated from all the water sources around the world (streams, rivers, ponds, seas, oceans etc).
It is am established fact that the quantity of water present on the Earth has remained constant from the beginning of time. At any given point in time it may exist in one of its three forms i.e.ice, water or water vapor but there is no variation in its total quantity (hydrological cycle).

From our previous experiment, we examined how many drops a penny can hold - and place drops of salt water on the penny after recording 5 trials each, take the average of each solution.