Answer
There are 3 significant digits.
Work Step by Step
To find the number of significant digits in the measurement $41,\bar{0}00 $ mi, we follow the rules on page 162 of the book.
We use rule #1: all non-zero digits are significant. Thus "4, 1" are significant.
We also use rule #3: the tagged zeros are significant; that is, the tagged zero here is significant.
Thus, there are 3 significant digits.
