[填空题]
The decay rate of radium-k ubctp. q:;96 ix4fim 226 , a naturally occurring radirj cr*ax6 1 . :f8gwev(ypdyv4oactive metal, is directly proportional to the amount observed at that instant. The half-ligvryw4(:r j*1vxafe 6.dpyc 8fe of radium-226 is 1600 years. At an initial measurement, there was 100 grams of radium-226 in a sample.
1. Find an expression for the amount of radium-226, R , in the sample in terms of t , where t is the time in years after the initial measurement.
R(t)=ae$^{-0.000433t}$;a= .
2. Find to the nearest gram the amount of radium- 226 in the sample after 3000 years.
R(3000)≈ grams.(round number)
