How to use standard form and round to significant figures on the Casio fx-CG50, TI-84 Plus CE and TI-Nspire CX II
On the fx-CG50: SHIFT MENU (SET UP) → Display → Sci.On the TI-84 Plus CE: mode → SCI.On the TI-Nspire CX II: home/on → Settings → Document Settings.
Type numbers like 3.2 × 10⁵ correctly, show answers in standard form and round to 3 significant figures without losing accuracy. Exact keystrokes for the fx-CG50 first, then the other calculators, a worked example you can check your answers against, the mistakes that cost marks, and the same thing in Desmos.
When you need it
Standard form (a × 10k, 1 ≤ a < 10) is in SL 1.1 for both AA and AI, and every calculator answer needs rounding: exact or 3 significant figures unless the question says otherwise. Rounding too early is one of the most common ways to lose an accuracy mark.
Practise it: Scientific notation (AI SL) · SL AI approximations and error.
Which IB course and paper
| Course | GDC papers | What you use it for |
|---|---|---|
| AA SL | Paper 2 (Paper 1 is calculator-free) | Operations with numbers in the form a × 10^k, and rounding answers. |
| AA HL | Papers 2 and 3 (Paper 1 is calculator-free) | As SL. |
| AI SL | Papers 1 and 2 | Operations with numbers in the form a × 10^k, rounding, and approximation and percentage error. |
| AI HL | Papers 1, 2 and 3 | As SL. |
A GDC is allowed on every AI paper and on AA Papers 2 and 3; AA Paper 1 is calculator-free, so learn the method by hand as well.
Topic notes: Scientific notation and estimation (AI SL).
Keystrokes on your calculator
Pick your calculator: the page remembers it next time.
Standard form and rounding on the Casio fx-CG50
Written for OS 3.80 (menus unchanged from OS 3.60 onwards as far as we can tell). Casio fx-CG50: graphic (GDC).
- MENU 1 (RUN-MATRIX). Type 3.2 ×10ˣ 5 × 4.5 ×10ˣ (−) 2 EXE: 14400.
- To show answers in standard form: SHIFT MENU (SET UP), move down to Display, choose Sci and enter the number of significant figures (3; 0 means 10). EXIT.
- Back to normal: SET UP → Display → Norm.
- Fix, Sci and Norm change only the display: internally the calculator still uses a 15-digit mantissa.
Standard form and rounding on the TI-84 Plus CE
Written for OS 5.8.x. TI-84 Plus CE: graphic (GDC); also the TI-84 Plus CE Python / CE-T Python Edition.
- Type 3.2 2nd , (EE) 5 × 4.5 2nd , (−) 2 enter: 14400. On screen 3.2E5 means 3.2 × 10⁵.
- To show answers in standard form: mode, choose SCI on the NORMAL SCI ENG line, and 2 on the FLOAT line (2 decimal places, so 3 significant figures in SCI). 2nd mode (QUIT).
- The answer shows as 1.44E4: write it as 1.44 × 10⁴.
- Set NORMAL and FLOAT again afterwards, or every later answer is rounded to 2 decimal places.
Standard form and rounding on the TI-Nspire CX II
Written for OS 6.x. TI-Nspire CX II: graphic (GDC), non-CAS; the CX II CAS is not allowed in IB, A Level or IGCSE exams.
- On a Calculator page type 3.2·10^5·4.5·10^(−2) and enter: 14400.
- To show answers in standard form: home/on → Settings → Document Settings, set Exponential Format to Scientific. Display Digits sets how many digits you see (Float, Float1 to Float12, Fix0 to Fix12).
- The answer shows as 1.44E4: write it as 1.44 × 10⁴.
For teachers: Show on the board Print a keystroke card Teaching GDC skills
Worked example
(a) Work out (3.2 × 10⁵) × (4.5 × 10⁻²) in standard form. (b) Work out (6.02 × 10²³) ÷ (3.1 × 10⁴), giving your answer in standard form to 3 significant figures. (c) Round 0.00456782 to 3 significant figures and write it in standard form.
Answers (checked with Python)
(a) 14400 = 1.44 × 10⁴. (b) 1.9419… × 10¹⁹ = 1.94 × 10¹⁹ (3 s.f.). (c) 0.00457 = 4.57 × 10⁻³ (the zeros after the decimal point are not significant).
Common calculator mistakes
- Writing the calculator's E notation (1.44E4) as the answer: write 1.44 × 10⁴.
- Typing powers of ten as × 10 ^ without brackets in a division: (6.02 × 10²³) ÷ (3.1 × 10⁴) needs the brackets, or use the ×10ˣ key.
- Rounding in the middle of a calculation: keep the full value (Ans or a stored letter) and round only the final answer.
- Counting the zeros at the start of 0.00456782 as significant figures: 3 s.f. is 0.00457.
- Leaving Sci or Fix switched on for the next question, which then shows rounded values you did not ask for.
- Accuracy: unless the question says otherwise, IB markschemes want answers exact or to 3 significant figures. Keep the full calculator value for later parts and round only the answer you write down (x = 2.094551… is written 2.09, not 2.1 or 2.0946).
If you get an error
fx-CG50: Ma ERROR
Ma ERROR Casio's Math ERROR: the result is outside the allowable calculation range, or you are trying to do an illegal mathematical operation, such as dividing by zero. Check: Look for a zero denominator, sin⁻¹ or cos⁻¹ of a number bigger than 1 (often a wrong side or angle in the sine or cosine rule), the log of 0 or of a negative number, and a value stored in a variable earlier that you forgot about. Fix: Casio's advice: check your input values and change them so the result is within the allowable range.
TI-84 Plus CE: ERR:DOMAIN, ERR:SYNTAX
ERR:DOMAIN A value given to a function or instruction is outside the values it accepts. In a regression, TI says it means the data do not suit the model you chose. Check: Is every input allowed? σ must be positive, p between 0 and 1, and sin⁻¹ or cos⁻¹ needs a number from −1 to 1. Exponential and power models need positive data. Fix: Change the value that is out of range, or choose a model that suits the data.
ERR:SYNTAX The command contains a syntax error: a misplaced function, argument, bracket or comma. Check: TI points out that subtract − and negative (−) are different keys, and using the wrong one causes this error. Then check the brackets and commas. Fix: Find the misplaced function, argument, bracket or comma and correct it.
TI-Nspire CX II: Domain error, Syntax error
Domain error An argument must be in a specified domain, and this one is not (TI's example: rand(0)). Check: Is every input allowed? σ must be positive, p between 0 and 1, and sin⁻¹ or cos⁻¹ needs a number from −1 to 1. Fix: Change the value that is out of range.
Syntax error The syntax checker found a problem. Check: A missing bracket or comma. Fix: Correct the expression and try again.
Do it in Desmos
Not in the exam. Desmos is not an approved calculator for IB exams, so never rely on it for Paper 2. It is excellent for learning, checking a GDC answer and building graphs for your Internal Assessment (IA).
- Type the calculation with brackets: (3.2·10^5)(4.5·10^(−2)).
- Desmos shows very large and very small answers in standard form automatically (with ×10).
Open desmos.com/calculator (free, in any browser) and type:
(3.2·10^{5})(4.5·10^{-2})frac{6.02·10^{23}}{3.1·10^{4}}
Questions
Can I use a calculator for standard form and rounding in the exam?
In IB Maths you can use one approved GDC on every AI paper and on AA Papers 2 and 3, in exam mode. AA Paper 1 is calculator-free, so learn the method by hand as well.
What are the fx-CG50 keystrokes for standard form and rounding?
MENU 1 (RUN-MATRIX). Type 3.2 ×10ˣ 5 × 4.5 ×10ˣ (−) 2 EXE: 14400. Then To show answers in standard form: SHIFT MENU (SET UP), move down to Display, choose Sci and enter the number of significant figures (3; 0 means 10). EXIT. Then Back to normal: SET UP → Display → Norm. The full steps and the other calculators are in the keystrokes section above.
Does this work on other calculators?
Yes. This page has keystrokes for the Casio fx-CG50, TI-84 Plus CE and TI-Nspire CX II. The worked example has the same answers on every model, so use it to check.
What should I write as working?
Write the maths, not the key presses: say what you are finding in normal notation (the equation, the probability statement or the integral), then the calculator's answer exact or to 3 significant figures unless the question says otherwise. Keep full accuracy in later parts.
More calculator skills
What else is free here
- Every syllabus topicA page for each AA and AI sub-topic, with exam-style questions and mark schemes.
- GDC keystrokes by topicTI-Nspire and Casio fx-CG50 guides for the calculator papers.
- Casio fx-CG50 guideEvery menu you need for IB Maths and the exam traps, on one page.
- Free formula sheets (PDF)One page per course, marking which formulas are not in the IB booklet.
Save your scores and practise the questions that use thisA free account remembers the questions you have done and brings you back to this page.
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Sources
- Casio fx-CG50 Software User's Guide, OS 3.70 (PDF) : Casio fx-CG50, OS 3.80 (menus unchanged from OS 3.60 onwards as far as we can tell).
- TI-84 Plus CE guidebook (Texas Instruments) : TI-84 Plus CE, OS 5.8.x.
- TI-Nspire CX II guidebooks (Texas Instruments) : TI-Nspire CX II, OS 6.x.
- Desmos Help Center for the Desmos functions.
Menu names are taken from each manufacturer's manual for the models shown. Menus can move slightly between OS updates: if a screen looks different on yours, the manual for your version is the reference, and please tell us so we can update this page. A calculator with no tab here has no checked steps for this skill yet. Worked-example answers were recomputed independently in Python.