Significant Figures Practice Worksheet - Free Printable

Let's solve the Significant Figures Practice Worksheet step by step. We'll determine how many significant figures each number has, based on the standard rules for significant figures.

---

🔢 Rules for Significant Figures:

1. All non-zero digits are significant.
2. Zeros between non-zero digits are significant.
3. Leading zeros (before the first non-zero digit) are NOT significant.
4. Trailing zeros (after the last non-zero digit):
- Are significant only if there is a decimal point.
- If no decimal point, trailing zeros may be ambiguous (but in this context, we assume they're not significant unless specified).
5. In scientific notation, only the digits in the coefficient count as significant.

---

Now let’s go through each problem:

---

1) 1234
→ All digits are non-zero → 4 significant figures
✔ Answer: 4

2) 0.023
→ Leading zeros are not significant; 2 and 3 are → 2 significant figures
✔ Answer: 2

3) 890
→ No decimal point → trailing zero is not significant → only 8 and 9 → 2 significant figures
✔ Answer: 2

4) 91010
→ No decimal point → trailing zero is not significant → 9, 1, 0, 1 → the zero is between non-zeros → it is significant
→ So: 9, 1, 0, 1 → 4 digits → but last zero is trailing with no decimal → not significant
Wait! Let's clarify:
Digits: 9-1-0-1-0 → the middle zero is between non-zeros → significant
Last zero is trailing with no decimal → not significant
So significant digits: 9, 1, 0, 1 → 4 significant figures
✔ Answer: 4

5) 9010.0
→ Has decimal point → trailing zeros are significant
→ All digits: 9, 0, 1, 0, .0 → all are significant?
- 9 → yes
- 0 (between 9 and 1) → yes
- 1 → yes
- 0 (before decimal) → after 1 → but it's followed by decimal → so it's significant
- Final .0 → significant
→ So: 5 significant figures
✔ Answer: 5

6) 1090.0010
→ All digits: 1, 0, 9, 0, ., 0, 0, 1, 0
- Leading zeros? None
- Zeros between non-zeros → significant
- Trailing zeros after decimal → significant
→ Every digit is significant → 9 digits → 9 significant figures
✔ Answer: 9

7) 0.00120
→ Leading zeros: not significant
→ First non-zero: 1 → then 2 → then 0 (trailing after decimal) → significant
→ So: 1, 2, 0 → 3 significant figures
✔ Answer: 3

8) 3.4 × 10⁴
→ Coefficient: 3.4 → two digits → both significant
→ Exponent doesn't affect sig figs
✔ Answer: 2

9) 9.0 × 10³
→ Coefficient: 9.0 → the zero is after decimal → significant
→ So: 9 and 0 → 2 significant figures
✔ Answer: 2

10) 9.010 × 10⁻²
→ Coefficient: 9.010 → all digits are significant
→ 9, 0, 1, 0 → four digits → 4 significant figures
✔ Answer: 4

11) 0.00030
→ Leading zeros: not significant
→ First non-zero: 3 → then 0 → trailing zero after decimal → significant
→ So: 3 and 0 → 2 significant figures
✔ Answer: 2

12) 1020010
→ No decimal point → trailing zeros may not be significant
→ But let's look: 1, 0, 2, 0, 0, 1, 0
→ The zeros between non-zeros:
- Between 1 and 2 → significant
- Between 2 and 1 → significant
- After 1 → trailing → no decimal → not significant
→ So: 1, 0, 2, 0, 1 → five digits → 5 significant figures
✔ Answer: 5

13) 780.
→ Note: There is a decimal point at the end → trailing zero is significant
→ So: 7, 8, 0 → all three are significant
✔ Answer: 3

14) 1000
→ No decimal point → trailing zeros not significant
→ Only 1 is significant → 1 significant figure
✔ Answer: 1

15) 918.010
→ Decimal present → all digits significant
→ 9, 1, 8, 0, 1, 0 → six digits → 6 significant figures
✔ Answer: 6

16) 0.0001
→ Leading zeros → not significant
→ Only 1 → 1 significant figure
✔ Answer: 1

17) 0.000390
→ Leading zeros → not significant
→ 3, 9, 0 → trailing zero after decimal → significant
→ So: 3, 9, 0 → 3 significant figures
✔ Answer: 3

18) 8120
→ No decimal point → trailing zero → not significant
→ Digits: 8, 1, 2 → 3 significant figures
✔ Answer: 3

19) 7.991 × 10¹⁰
→ Coefficient: 7.991 → four digits → all significant
→ 4 significant figures
✔ Answer: 4

20) 72
→ Both digits non-zero → 2 significant figures
✔ Answer: 2

---

✔ Final Answers:

1) 4
2) 2
3) 2
4) 4
5) 5
6) 9
7) 3
8) 2
9) 2
10) 4
11) 2
12) 5
13) 3
14) 1
15) 6
16) 1
17) 3
18) 3
19) 4
20) 2

---

Let me know if you'd like this formatted as a printable answer key!