Work Step by Step
Apply the rules on page 162 of the book to find the significant digits (the accuracy) of the measurement 0.0070 W. We use rule #1: all non-zero digits are significant. Thus "7" is significant. Rule #4 states that all zeros to the right of a significant digit and the decimal point are significant and so we have a zero to the right of 7 that is significant. Rule #6 tells us to ignore zeros to the left of the 7. Thus, there are 2 significant digits.