Worked answers

Significant Figures Examples with Answers

Fast worked examples for the exact numbers students search: 100, 1000, 0.00450, 90.010, and common rounding questions.

Significant figures example cards for counting and rounding

How Many Significant Figures Are in 0.020?

0.020 has 2 significant figures: the 2 and the final zero after the decimal. See the digit-by-digit rule, scientific notation, and common mistakes.

0.020 has 2 significant figures.

Counting

How Many Significant Figures Are in 100?

100 usually has 1 significant figure when written without a decimal point. Learn why the trailing zeros are ambiguous and how to show 2 or 3 sig figs clearly.

100 has 1 significant figure.

Counting

How Many Significant Figures Are in 1000?

1000 usually has 1 significant figure when written without a decimal point. Learn why the three zeros are ambiguous and how to show 2, 3, or 4 sig figs.

1000 has 1 significant figure by default.

Counting

How Many Significant Figures Are in 0.00450?

0.00450 has 3 significant figures: 4, 5, and the final zero. See which zeros count, why the leading zeros do not, and how to write it in scientific notation.

0.00450 has 3 significant figures.

Counting

How Many Significant Figures Are in 0.00208?

0.00208 has 3 significant figures because the middle zero is between non-zero digits.

0.00208 has 3 significant figures.

Counting

How Many Significant Figures Are in 90.010?

90.010 has 5 significant figures. Zeros between non-zero digits and trailing decimal zeros count.

90.010 has 5 significant figures.

Rounding

Round to 2 Significant Figures

Learn how to round any number to 2 significant figures with clear rules, worked examples, and common mistakes for decimals, whole numbers, and scientific notation.

Keep the first two significant digits, then use the next digit to decide whether to round up or down.

Rounding

Round to 3 Significant Figures

Learn how to round any number to 3 significant figures with clear steps, worked examples, and common mistakes for decimals, whole numbers, and scientific notation.

Keep the first three significant digits, then use the fourth significant digit to decide whether to round up or down.

Rounding

Round 7982 to 2 Significant Figures

7982 rounded to 2 significant figures is 8.0e+3, which avoids ambiguous trailing zeros.

7982 rounded to 2 significant figures is 8.0e+3.

Rounding

Round 0.9978 to 2 Significant Figures

0.9978 rounded to 2 significant figures is 1.0 because the next digit rounds 0.99 upward.

0.9978 rounded to 2 significant figures is 1.0.

Rounding

Round 0.83 to 1 Significant Figure

0.83 rounded to 1 significant figure is 0.8 because the next digit is less than 5.

0.83 rounded to 1 significant figure is 0.8.

Rounding

Round 123.456 to 3 Significant Figures

123.456 rounded to 3 significant figures is 123 because the fourth significant digit is 4.

123.456 rounded to 3 significant figures is 123.

Scientific Notation

Significant Figures in Scientific Notation

In scientific notation, significant figures are counted in the coefficient, not in the power of ten.

1.00e+3 has 3 significant figures.