The number 1.73 has three significant figures (1, 7, 3).
1.73 has 3 significant figures and 2 decimals. 1.73 rounded to 2 sig figs is 1.7, and to 1 sig figs is 2.
To count the number of sig figs in 1.73, count all 3 digits since it has no insignificant digits (all digits are significant).
