1. The problem asks to write numbers in standard form correct to three significant figures. 2. Standard form means expressing numbers as $a \times 10^n$ where $1 \leq |a| < 10$ and $n$ is an integer. 3. To round to three significant figures, identify the first three non-zero digits and round the number accordingly. 4. For example, if the number is 0.0045678, the first three significant figures are 4, 5, and 7. 5. Rounding 0.0045678 to three significant figures gives $4.57 \times 10^{-3}$. 6. Another example: 12345 rounded to three significant figures is $1.23 \times 10^{4}$. 7. Always express the final answer in the form $a \times 10^n$ with three significant digits in $a$. This method applies to any number you provide.