The Indian rupee dropped by 30 paise to a one-month low of 47 rupees 20 paise against the US dollar on the back of persistent demand from importers and banks as the American currency firmed up overseas. The domestic unit opened lower at 46 rupees 93 paise per dollar against yesterday's close of 46 rupees 91 paise per dollar and fell further to qouto at 47 rupees 6 paise per dollar.