Question

how many significant figures are in this number? 500

Explanation:

Step1: Recall Significant Figure Rules

For a number like 500, trailing zeros in a whole number without a decimal are ambiguous, but the non - zero digit (5) and we consider the rules: non - zero digits are significant, and trailing zeros in a whole number without a decimal may or may not be significant, but in the case of 500, if we assume it's written as a whole number without indicating that the zeros are significant (no decimal), the significant figure is the non - zero digit. Wait, no, correction: The rule for significant figures: Non - zero digits are always significant. Zeros between non - zero digits are significant. Trailing zeros in a number without a decimal point are not significant (they are just placeholders), but if the number is written as 500., the trailing zeros would be significant. For 500 (without a decimal), the first non - zero digit is 5, and the two zeros are trailing zeros without a decimal, so they are not significant. Wait, no, another way: The number of significant figures in 500: the digit 5 is significant, and the zeros are trailing zeros in a whole number. If there is no decimal, the trailing zeros are not considered significant. But wait, sometimes, if the number is meant to have the zeros as significant, it would be written with a decimal (like 500.). But in the number 500 (as given), we follow the rule that trailing zeros in a whole number (without a decimal) are not significant. So the significant figure here is 1? Wait, no, that's a mistake. Wait, the correct rule: For numbers like 500, the number of significant figures depends on how it's presented. If it's written as 500 (without a decimal), the significant figure is 1 (only the 5). But wait, some sources say that if the number is written as 500, and we assume that the zeros are just placeholders, then the significant figures are 1. But wait, maybe I was wrong. Wait, let's re - check: The rules for significant figures:

1. All non - zero digits are significant.
2. Zeros between non - zero digits are significant.
3. Zeros at the end of a number (trailing zeros) are significant only if the number contains a decimal point.

So for 500 (no decimal), the trailing zeros are not significant. So the only significant digit is 5. So the number of significant figures is 1. Wait, but that seems counter - intuitive. Wait, another example: 50 has 1 significant figure (the 5), 500 has 1, 5000 has 1. But if it's 5.00, then it has 3 significant figures. If it's 500., then it has 3. So in the case of 500 (no decimal), the significant figures are 1.

Step2: Apply the Rule to 500

The number is 500, no decimal point. The non - zero digit is 5, and the two zeros are trailing zeros without a decimal, so they are not significant. So the number of significant figures is 1. Wait, but I think I made a mistake earlier. Wait, no, let's confirm with a reference: According to significant figure rules, trailing zeros in a whole number (without a decimal) are not significant. So 500 has 1 significant figure.

Answer:

1