Posting its fifth straight day of losses, the Sensex at the Bombay Stock Exchange suffered another big fall of 468 points, or 2.4 percent, to close at a six-week low of 19,224, today. The Sensex tumbled on sustained selling by investors spooked by fears of an interest rate hike by the Reserve Bank, and amid weak Asian and European markets. The Nifty at the National Stock Exchange slipped 142 points, or 2.4 percent, to 5,763.Stock markets in China, Hong Kong, South Korea and Singapore dropped between 0.3 percent and 1.7 percent.