Answer
$400$
Work Step by Step
First, we must determine the common ratio between the terms:
$r=\frac{-0.004}{0.0004}=\frac{0.04}{-0.004}=\frac{-0.4}{0.04}=-10$
For solving this, we will use the formula for the $nth$ term of the geometric series. $a_{n}=a_{1}\times r^{n-1}$. Then put correct value for $7th$ term to solve.
$a_{7}=0.0004 \times (-10)^{7-1}=400$
