Significant Figures Practice Quiz – Answer Key & Explanations
Here is the complete answer key and detailed explanations for counting significant figures. Use this to check your work and reinforce the rules!
The 3 Core Rules (Quick Recap)
1. Non-zero numbers always count. (e.g.,   3 sig figs)
2. Sandwiched zeros always count. Zeros between non-zero digits count. (e.g.,   3 sig figs)
3. Zeros at the end only count IF there is a visible decimal point.
 Leading zeros (at the very beginning) never count—they are just placeholders.
Answer Key
Question
Number
Correct Sig Figs
Step-by-Step Explanation
1
0.00702
3
• The leading zeros (0.00) at the start do not count. • The zero sandwiched between 7 and 2 does count. • Digits that count: 7, 0, 2.
2
4,500
2
• The non-zero digits (4 and 5) count. • The two zeros at the end do not count because there is no visible decimal point. • Digits that count: 4, 5.
3
30.00
4
• The non-zero digit (3) counts. • All trailing zeros count because a decimal point is explicitly present. • Digits that count: 3, 0, 0, 0.
4
808.0
4
• The non-zero digits (8 and 8) count. • The zero between the eights counts (sandwiched). • The trailing zero after the decimal counts. • Digits that count: 8, 0, 8, 0.
5
0.03050
4
• The leading zeros (0.0) do not count. • The non-zero digits (3 and 5) count. • The zero between 3 and 5 counts (sandwiched). • The trailing zero at the very end counts because of the decimal point. • Digits that count: 3, 0, 5, 0.
Self-Check Summary
 5 / 5 Correct: You've mastered counting significant figures!
 3 – 4 Correct: You're very close! Pay close attention to trailing zeros with vs. without decimals.
 Under 3 Correct: Review the rule for leading zeros ( never count) and try a few more practice problems.
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