Question

Round off the following numbers to three significant figures.
40.009????????

Answer 1

40.0

40.009 contains 5 significant figures and 3 decimals. 40.009 rounded to 4 sig figs is 40.01, to 3 sig figs is 40.0, and to 2 sig figs is 40.. To count the number of sig figs in 40.009, count all 5 digits since it has no insignificant digits (all digits are significant).