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.
Precipitation. Condensed water vapor that falls to the Earth's surface. Most precipitation occurs as rain, but also includes snow, hail, fog drip, graupel, and sleet. Approximately 505,000 km 3 (121,000 cu mi) of water falls as precipitation each year, 398,000 km 3 (95,000 cu mi) of it over the oceans.