Final answer:
The number 8.60 x 10⁴ has three significant figures, as all digits in the scientific notation are counted as significant except for leading, placeholder, or trailing zeros that are placeholders.
Step-by-step explanation:
The number 8.60 x 10⁴ has three significant figures. In scientific notation, significant figures are those digits that carry meaning contributing to its precision. This includes all the digits except: any leading zeros, placeholder zeros, and trailing zeros when they are merely placeholders to indicate the scale of the number. With scientific notation, all digits expressed are considered significant. Here, 8.60 indicates three significant figures because the zero after the decimal point indicates a measure of precision, and 10⁴ simply serves to locate the decimal point but does not affect the number of significant figures.