To divide one power of ten by another, simply subtract the two exponents (see Multiplication/Division). Next, convert the two numbers from scientific notation to real numbers. Now add the two numbers normally. Finally convert to scientific notation if the coefficient is less than 1 or greater than 10.
Precipitation occurs when cloud droplets combine and grow large enough to fall to the earth the rate of evaporation as a drop falls to the earth also can affect its size. from: sadia aisa.
It is the common process by which atmospheric water becomes surface, or subsurface water. The term precipitation is also commonly used to designate the quantity of water that is precipitated. Precipitation includes rainfall, snow, hail, and sleet, and is therefore a more general term than rainfall.