The rupee today strengthened by 15 paise to trade at 55 ruppe 33 paise against the US dollar in early trade as the American currency weakened against other currencies overseas. In addition, dollar selling by banks and exporters and a higher opening in the equity market also supported the rupee.The rupee had lost 37 paise to close at 55 rupee 48 paise against the dollar yesterday on fresh dollar demand from importers and banks.