Final answer:
To find the length of PR, measure the distance between points P and R using a ruler or measuring tape, ensuring that one end starts at P and the other end finishes at R.
Step-by-step explanation:
The length of PR can be determined by measuring the distance between points P and R. To measure this distance accurately, you can use a ruler or measuring tape. When measuring, make sure that one end of the ruler or tape lines up with point P, and then read the measurement at point R. The unit used for this measurement will depend on the context, but common units include centimeters, meters, or inches.