Mumbai, Dec. 16 -- The Indian rupee tumbled sharply to crash beyond Rs 91 per dollar mark on Tuesday tracking muted local equities and risk averse sentiments. Lingering uncertainty around tariffs coupled with persistent foreign portfolio outflows weighed on the local unit. INR opened at Rs 90.87 and hit a low of 91.14 before paring some losses to end at 90.93 as compared to previous close at 90.78. The Indian rupee extended its losing streak for the fourth trading day, hitting 91-per-dollar for the first time as the government tabled a bill in Lok Sabha to raise FDI in the insurance sector to 100 percent. The benchmark BSE Sensex dropped 533.50 points, or 0.63 percent, to 84,679.86, extending the previous session's decline amid weakness i...