(N/A) The rules for determining significant figures are as follows:
$(1)$ $(a)$ All non-zero digits are significant. For example,in $584$,there are $3$ significant figures.
$(b)$ All zeros between two non-zero digits are significant,regardless of the decimal point position. In $120007 \ cm$,the digits $1, 2, 0, 0, 0, 7$ are all significant,totaling $6$ significant figures.
$(c)$ Trailing zeros in a number without a decimal point are not significant. For example,in $12300 \ m$,the number of significant figures is $3$.
$(d)$ For numbers less than $1$,zeros to the right of the decimal point but to the left of the first non-zero digit are not significant. In $0.002308$,the leading zeros are not significant.
$(e)$ In a number with a decimal point,trailing zeros are significant. For example,in $3.500 \ cm$,there are $4$ significant figures. In $0.06990$,the leading zeros are not significant,but the trailing zero is significant,resulting in $4$ significant figures $(6, 9, 9, 0)$.
$(2)$ When measurements are represented with trailing zeros,it indicates higher precision; thus,they are significant. For example,$4.700 \ m = 470.0 \ cm = 4700 \ mm$ all have $4$ significant figures.
$(3)$ Scientific notation $(a \times 10^b)$ is the best way to remove ambiguity. Here,$a$ is a number between $1$ and $10$,and $b$ is an integer. For example,$246.35 \ kg$ is written as $2.4635 \times 10^2$.
$(4)$ The zero placed to the left of the decimal point in numbers like $0.5$ is not significant.
$(5)$ Exact numbers (like constants in formulas such as $S = 2\pi r$) have an infinite number of significant figures.