To express the number 0.000000003 in the form of \( a \times 10^n \), we need to write it as a value between 1 and 10 multiplied by a power of 10.
The number \( 0.000000003 \) can be converted as follows:
- Identify the decimal point: \( 0.000000003 \).
- Move the decimal point to the right until we have a number between 1 and 10. Moving the decimal point 9 places to the right gives us \( 3 \).
- Each time we move the decimal point to the right, we decrease the exponent of 10 by 1. Since we moved it 9 places, we have \( 3 \times 10^{-9} \).
Thus, the number can be expressed as:
\[ 3 \times 10^{-9} \]
So the correct response is:
3 × 10⁻⁹