How to use the finance (TVM) solver on the Casio fx-CG50
Compound interest, loans, annuities and depreciation with the time-value-of-money solver (IB AI). 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
AI SL and HL: compound interest, the value of an investment, loan repayments, the time to reach a target, and amortisation. The IB accepts the TVM solver as working if you write down the values you entered (N = 72, I% = 4.5, PV = −5000, …).
Practise it: SL AI financial mathematics · SL AI financial maths · SL AA financial maths.
Keystrokes on your calculator
Pick your calculator: the page remembers it next time.
Finance (TVM solver) 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, then choose FINANCIAL (highlight it and press EXE).
- F2 (COMPOUND INTEREST).
- Enter n = 72, I% = 4.5, PV = −5000, PMT = 0, FV = 0 (to be found), P/Y = 12, C/Y = 12, with EXE after each.
- Press the key for the unknown: F5 (FV). The result is shown; EXIT (or F1 REPEAT) returns to the inputs.
- Loan: n = 60, I% = 6, PV = 20000, FV = 0, P/Y = 12, C/Y = 12, then F4 (PMT): −386.66 (negative: money paid out). For n use F1 (n).
- F6 (AMT) after a loan gives the amortisation: the interest and principal in a given payment range.
- Payment timing (beginning or end of each period) is in SHIFT MENU (SET UP) → Payment: BGN / END. The IB normally uses END.
- The other Financial menus: F1 SIMPLE INTEREST, F3 CASH FLOW (NPV, IRR), F4 AMORTIZATION, F5 CONVERSION (nominal ↔ effective rates).
Finance (TVM solver) 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.
- apps → 1: Finance → 1: TVM Solver.
- N = 72, I% = 4.5, PV = −5000, PMT = 0, FV = 0, P/Y = 12, C/Y = 12, PMT: END.
- Move the cursor to FV and press alpha enter (SOLVE). A square marks the solved value.
- The Finance app's Σ Int( and Σ Prn( functions give interest and principal paid over a range of payments.
Finance (TVM solver) 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.
- Calculator page: menu → Finance → Finance Solver.
- Enter N, I(%), PV, Pmt, FV, PpY, CpY; leave the unknown blank or 0.
- tab to the unknown and press enter to solve it.
- amortTbl( in the same menu builds an amortisation table.
Worked example
(a) $5000 is invested at 4.5% per year compounded monthly. Find its value after 6 years. (b) A $20 000 loan at 6% per year compounded monthly is repaid monthly over 5 years. Find the repayment and the total paid. (c) How long does money take to double at 5% compounded quarterly?
Answers (checked with Python)
(a) FV = $6546.52. (b) PMT = $386.66 per month; total $23199.36. (c) N = 55.8 quarters, so 14 years (13.9 years).
Common calculator mistakes
- Signs: money you pay (a deposit, a repayment) is negative; money you receive is positive. PV and FV with the same sign gives an error or nonsense.
- N is the number of periods, not years: 6 years monthly is 72.
- P/Y and C/Y must match the question (monthly payments with interest compounded yearly: P/Y = 12, C/Y = 1).
- Rounding money to 3 s.f.: give money to 2 decimal places (or as the question says).
- Not writing down the inputs: show N, I%, PV, PMT, FV, P/Y, C/Y as your working.
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).
- Graph the value against time in years: y = 5000(1 + 0.045/12)^{12x}.
- Evaluate it at x = 6, or add y = 10000 and click the intersection to see when it doubles.
- Desmos has no TVM solver; the formula is the same one your GDC uses.
The interactive graph loads here when you scroll to it.
Or open desmos.com/calculator and type:
y=5000(1+frac{0.045}{12})^{12x}5000(1+frac{0.045}{12})^{72}y=10000
More calculator skills
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 OS versions 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. Worked-example answers were recomputed independently in Python.