Final answer:
In the number 7000, the significant figure is the non-zero digit, 7. We need additional context, such as a decimal point or scientific notation, to determine if the zeros are significant. Without it, the zeros are assumed to be placeholders, not significant figures.
Step-by-step explanation:
Understanding significant figures is crucial in accurately reporting the precision of measurements. The determination of which digits are significant depends on a set of standard rules. All non-zero digits are always considered significant. Thus, in the number 7000, the digit 7 is without a doubt significant. However, the rule for zeros is that they are significant only if they are between significant digits, after a decimal point, or are at the end of a number with a decimal place. Since 7000 has no decimal point and the zeros are not between significant figures, they could be merely placeholders.
However, the ambiguity arises with whole numbers like 7000. Without additional context, such as scientific notation or a decimal point, we cannot determine if the zeros are significant or not. For example, if the number were given as 7000. or 7.000 × 10³, this would indicate that all the zeros are significant. But, in the given form '7000' without any further specification, we cannot automatically assume the zeros are significant. Therefore, assuming that the zeros are placeholders, the significant figure would be the non-zero digit -- 7.