Answer:
76.38 g
Explanation:
Below expresion can be used in calculating the remaining amount of radium
A(t)=A(0) (1/2)^(t/h)
Let A(t)=the remaining amount of radium
Let A(0)= amount of radium at the beginning= 90 grams
t= amount of time in years= 400 years
h=the half-life time= 1690 years
A(t)=A(0) (1/2)^(t/h)
If we substitute the values into the expresion we have
A(t) = 90 × (1/2)^(400/1690)
A(t)= 76.38 g