1. The problem is to express the number 2.15 multiplied by 10 raised to the power of -3 in standard decimal form. 2. The general formula for numbers in scientific notation is: $$a \times 10^n$$ where $a$ is the coefficient and $n$ is the exponent. 3. Here, $a = 2.15$ and $n = -3$. 4. A negative exponent means we divide by $10^3$, or equivalently move the decimal point 3 places to the left. 5. Moving the decimal point 3 places left in 2.15: $$2.15 \to 0.215 \to 0.0215 \to 0.00215$$ 6. Therefore, the number $2.15 \times 10^{-3}$ in decimal form is: $$0.00215$$