Answer: 216 hours
Step-by-step explanation: To convert 9 days into hours, we first start with the conversion factor for hours and days.
Conversion factor ⇒ 1 day = 24 hours
Next, notice that we are going from a larger unit "days" to a smaller unit "hours" and when we go from a larger unit to a smaller unit we multiply by the conversion factor.
So we multiply 9 by the conversion factor which is 24.
9 × 24 = 216
Therefore, Dr. Walker will collect her data for 216 hours.