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Quizzes > Science

Sig Figs Practice: Adding and Subtracting Significant Figures

Quick, free quiz on adding and subtracting sig figs. Instant results.

Editorial: Review CompletedCreated By: Roni BayuUpdated Aug 26, 2025
Difficulty: Moderate
2-5mins
Learning OutcomesCheat Sheet
Paper art illustration for sig figs addition and subtraction quiz on sky blue background

This quiz helps you practice adding and subtracting sig figs, so you can round sums and differences the right way in chemistry problems. Then build skills with sig figs practice, tackle multiplying and dividing sig figs, or review scientific notation and significant figures. Get quick feedback as you go.

What is the sum of 12.3 and 0.456, reported with the correct number of significant figures?
12.75
12.7
12.8
12.76
When adding or subtracting, the result is rounded to the least number of decimal places among the terms. 12.3 has one decimal place, while 0.456 has three. So the sum 12.756 is rounded to one decimal place as 12.8.
What is 2.345 minus 1.2, expressed with the correct significant figures?
1.145
1.14
1.15
1.1
Subtraction uses the least number of decimal places among the values: 2.345 has three decimal places, 1.2 has one. 2.345 ? 1.2 = 1.145, rounded to one decimal place gives 1.1.
Calculate 0.0045 + 0.00067 with the correct number of decimal places.
0.0051
0.0052
0.00520
0.00517
Align decimals and use the least decimal places: 0.0045 has four places, 0.00067 has five. Sum = 0.00517, rounded to four decimal places is 0.0052.
What is the result of adding 100. and 2.345, using proper decimal-place accuracy?
102.345
102.3
102.35
102
100. has zero decimal places, and 2.345 has three. Their sum is 102.345, rounded to zero decimal places gives 102.
Subtract 3.456 from 5.0 and report with correct precision.
1.6
1.5
1.54
1.544
5.0 has one decimal place; 3.456 has three. The raw difference is 1.544; rounding to one decimal place yields 1.5.
Add 1.23 and 4.1 with appropriate significant-figure rules.
5.4
5.3
5.33
5.30
1.23 has two decimal places; 4.1 has one. Sum = 5.33, rounded to one decimal place is 5.3.
What is 0.12 + 0.8, reported correctly?
0.9
0.920
0.90
0.92
0.12 has two decimal places; 0.8 has one. Sum = 0.92, rounded to one decimal place is 0.9.
Add 15.67 and 0 (an exact number). What is the result with correct precision?
15.67
15.7
15.6
15.670
Exact numbers (like 0) do not limit precision. The result retains the decimal places of 15.67. So the answer is 15.67.
What is the sum of 0.00230 and 0.0011 with proper decimal-place rounding?
0.0035
0.00330
0.00340
0.0034
0.00230 has five decimal places, 0.0011 has four; use four decimal places. Sum = 0.00340, rounded to four places is 0.0034.
Calculate 10.00 minus 9.111, reporting the result correctly.
0.890
0.89
0.889
0.9
10.00 has two decimal places, 9.111 has three; use two decimal places. Difference = 0.889, rounded to two places is 0.89.
What is 1.250 + 2.5 + 3.05, with correct significant-figure rules applied?
6.80
6.8
6.805
6.81
Decimal places: 1.250 (3), 2.5 (1), 3.05 (2). Use one decimal place. Sum = 6.80, rounded to one place is 6.8.
Add 123.4 and 0.0567; what is the correct result?
123.5
123.46
123.4567
123.45
Decimal places: 123.4 (1), 0.0567 (4). Use one decimal place. Sum = 123.4567, rounded to one place gives 123.5.
What is 2.0 ? 0.3456 reported correctly?
1.654
1.7
1.65
1.6544
Decimal places: 2.0 (1), 0.3456 (4). Use one decimal place. Difference = 1.6544, rounded to one place is 1.7.
Perform (1.2 + 2.34) ? 0.12 and report to proper precision.
3.4
3.42
3.54
3.42
First 1.2+2.34=3.54, use one decimal place (3.5). Then 3.5?0.12 with one decimal place gives 3.4.
What is the sum of 0.500 and 1.003 with correct decimal places?
1.5030
1.5
1.50
1.503
Both have three decimal places, so keep three. Sum = 1.503.
Calculate 7.89 + 0.011 + 0.4567 with proper sig-fig rounding.
8.358
8.36
8.4
8.3577
Decimal places: 7.89 (2), 0.011 (3), 0.4567 (4). Use two decimal places. Sum = 8.3577, rounded to two places is 8.36.
What is 12.345 + 0.67 + 0.0045, reported correctly?
13.02
13.019
13.0195
13.0
Decimal places: 12.345 (3), 0.67 (2), 0.0045 (4). Use two decimal places. Sum = 13.0195, rounded to two places is 13.02.
Compute (20.0 ? 0.345) + 1.23 with correct decimal places.
21.0
20.93
20.8
20.9
20.0?0.345=19.655, use one decimal place ? 19.7. Then 19.7+1.23, use one decimal ? 20.93 rounds to 20.9.
What is 100.5 + 2.345 ? 3.456 with proper rounding?
99.344
99.300
99.3
99.34
100.5+2.345=102.845 (one decimal ?102.8). Then 102.8?3.456=99.344, rounding to one decimal gives 99.3.
Add 0.1234, 1.2, and 3.45; report the result correctly.
4.77
4.77
4.8
4.7734
Decimal places: 0.1234 (4), 1.2 (1), 3.45 (2). Use one decimal place. Sum = 4.7734, rounded to one place is 4.8.
What is 2.34 minus 5.678, with proper significant-figure rounding?
-3.338
-3.3
-3.34
-3.340
Decimal places: 2.34 (2), 5.678 (3). Use two decimal places. Difference = -3.338, rounded to two places is -3.34.
Add 0.005678 and 0.00012 with correct decimal-place accuracy.
0.005798
0.0058
0.00579
0.00580
Decimal places: 0.005678 (6), 0.00012 (5). Use five places. Sum = 0.005798, rounded to five places is 0.00580.
What is (5.00 + 0.200) ? (3.0 + 1.234) with proper rounding?
1.00
1.000
1.0
1
5.00+0.200=5.200 (two decimals?5.20); 3.0+1.234=4.234 (one decimal?4.2). Then 5.20?4.2=1.00, reported with two decimals is 1.00.
What is the sum of 0.004560, 0.02340, and 1.200 with correct precision?
1.2280
1.228
1.23
1.22796
Decimal places: 0.004560 (6), 0.02340 (5), 1.200 (3). Use three decimal places. Sum = 1.2280, rounded to three places gives 1.228.
Compute (1000 ? 1.25) + 0.007, using correct decimal-place rules.
999
998.757
998.8
999.007
1000 has zero decimal places; subtracting 1.25 ? 998.75 rounds to 0 decimal places = 999. Then adding 0.007 (three decimals) keeps zero decimal places: 999.
0
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Study Outcomes

  1. Understand Sig Fig Addition Rules -

    Learn how to determine the correct number of significant figures when adding measurements by identifying decimal place limitations.

  2. Apply Proper Rounding Techniques -

    Practice rounding sums to the appropriate decimal place based on the least precise measurement in your calculations.

  3. Analyze Sig Fig Subtraction Scenarios -

    Examine subtraction problems to ensure the result reflects the precision dictated by the original data.

  4. Perform Real-World Calculations -

    Use addition and subtraction with significant figures to solve applied examples, reinforcing how to add and subtract with significant figures.

  5. Evaluate Calculation Precision -

    Assess the accuracy of results by checking that the correct rules of significant figures for subtraction and addition are followed.

  6. Build Confidence with Quiz Practice -

    Test your mastery through targeted questions, boosting your skill in sig figs addition and subtraction.

Cheat Sheet

  1. Align Decimal Points and Identify the Least Precise Value -

    In sig figs addition and subtraction, always line up the decimal points before calculating and find the measurement with the fewest decimal places; this dictates your final precision. For instance, when adding 12.11 + 18.0 + 1.013, the least precise value has one decimal place, so round your result to one decimal place (31.1) per NIST guidelines.

  2. Use Decimal Places, Not Significant Digits, for Rounding -

    Unlike multiplication or division, addition in significant figures focuses on decimal places rather than total sig figs. Always round your sum or difference to the same number of decimal places as the measurement with the fewest decimals, ensuring accuracy in scientific reporting.

  3. Apply the Final Rounding Rule Mindfully -

    When you calculate the exact sum or difference, save rounding until the end to maintain precision - this is key to mastering sig fig for addition. A handy mnemonic is "Left's Least, Round Fast": look left to the least precise decimal place, then round your final answer based on that position.

  4. Convert to Scientific Notation for Consistency -

    For clear guidance on how to add and subtract with significant figures, rewrite each value in scientific notation first; match exponents, perform the operation, then round by decimal-place rules. This method from university chemistry guidelines simplifies complex additions like (3.45×10^2)+(2.1×10^2)=5.55×10^2, rounded to 5.6×10^2.

  5. Watch for Ambiguous Trailing Zeros -

    Trailing zeros in a whole number can hide true precision - clarify by adding a decimal point or switching to scientific notation when practicing significant figures for subtraction or addition. For example, stating 1500 as 1.500×10^3 (per UC Berkeley standards) shows four significant digits and avoids confusion in subsequent calculations.

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