12.5g. One kilogram is equal to 1000 kilograms, and one kilogram contains 25 kilograms of materials. According to the mathematical unit, 1000 kg contains 25 kg of materials, and 25 divided by 10000 equals 0.025. Find the number of grams put in a catty. A catty equals 500 grams, and 0.025 times 500 equals 65438+. The first-class Chinese character (commonly used word) gram in the Pinyin kè of the General Standard of Chinese was first seen in Oracle Bone Inscriptions.