The answer is **0.0082**.

To round 0.00821 to two significant digits, start with the first significant digit, which is the 8. Then count to the right from there.

The zeros between the decimal point and the 8 are not significant, as they serve only to "place" the 8 into the thousands place. It provides no information about the accuracy of the following digits.

The first two significant digits of 0.00821 are the 8 and the 2. Just to the right of the 2 is a 1. Because this value is "4 or less", we do not round up. Drop everything that follows.

To determine what numbers are significant and which aren't, use the following rules:

## 1. The zero to the left of the decimal value less than 1 is not significant.

## 2. All trailing zeros that are placeholders are not significant.

## 3. Zeros between non zero numbers are significant.

## 4. All non zero numbers are significant.

## 5. If a number has more numbers than the desired numbers of significant digits, the number is rounded. For example, 432,500 is 433,000 to 3 significant digits.

## Zeros at the end of numbers which are not significant but are not removed, as removing would affect the value of the number. In the above example, cannot remove 000 in 433,000 unless changing the number into scientific notation.

Learn more about significant digits from the following links:

## www.omnicalculator.com

## www.bbc.co.uk

## www.purplemath.com