Question 3
The measurement $9.0 \times 103 \mathrm{~km}$ has significant figures. ANSWERING INSTRUCTIONS: In your answer, do not s word; instead use a number. For example instead of typing "forty", instead use the number 40.

Step 1 ：The significant figures in a number are digits that carry meaningful information about its precision. In the given measurement $9.0 \times 10^3 \mathrm{~km}$, the significant figures are the digits in the number before the exponential part.

Step 2 ：The number 9.0 has two significant figures: the 9 and the 0 after the decimal point.

Step 3 ：The 3 in the exponent is not considered a significant figure because it is part of the exponential notation, which indicates the order of magnitude, not the precision of the number.

Step 4 ：Final Answer: The number of significant figures in the measurement $9.0 \times 10^3 \mathrm{~km}$ is \(\boxed{2}\).