To find the value of \( A(15) \) using the equation \( A(t) = 10(3)^{0.2t} \), we simply need to substitute \( t = 15 \) into the equation.
\[ A(15) = 10(3)^{0.2 \times 15} \]
Calculating \( 0.2 \times 15 \):
\[ 0.2 \times 15 = 3 \]
Now we can substitute this value back into the equation:
\[ A(15) = 10(3)^{3} \]
Next, we calculate \( 3^3 \):
\[ 3^3 = 27 \]
Now substitute this value back into the equation:
\[ A(15) = 10 \times 27 = 270 \]
Thus, the value for \( A(15) \) is:
\[ \boxed{270} \]