From its name of 18 carat gold you can tell, if it is truly 18 carat gold, that there is 18/24ths gold and 6/24ths of another metal, possibly copper or platinum. 18 carat gold is (18/24)x100= 75%...
Your question is not clear. Is it referring to Diamond carat or Gold karat. This is because both have different meaning. While, Carat refers to weight of diamond (or gemstones), Karat refers to...