The Sensex at the Bombay Stock Exchange slumped 275 points, or 1.7 percent, to 16,213, on worries about slowing GDP growth, and amid weak Asian markets, on Friday. The Nifty at the National Stock Exchange declined 77 points, or 1.6 percent, to 4,867.Stock markets in Japan, China, Hong Kong, South Korea and Singapore lost between 0.6 percent and 2.7 percent, as concerns persisted about the euro-zone debt crisis.