Calculator guide

Which one to buy, which buttons matter, and where students consistently lose marks.

What you're allowed in the exam

• UK A-Level: any scientific or graphic calculator without symbolic algebra (CAS) or a wireless data connection. Fx-991EX + fx-CG50 both fit.
• Edexcel IAL: same rules — non-CAS, non-networked. Casio fx-991EX/ES/CG50 or TI-Nspire CX are the common ones. P1 (WMA11) is the one non-calculator IAL paper — no calculator at all; P2, P3, P4, S1, M1 (and M2, S2, D1) all permit one.
• UK A-Level (9MA0): all three papers permit a calculator.
• Not allowed: anything labelled "CAS", "TI-89 Titanium", "TI-Nspire CX CAS", or with a QWERTY keyboard.

The 5 buttons that lose kids marks

1. Radians vs Degrees. Every calculator has a mode indicator (R / D / G). Check it at the start of every trig question. Losing 3 marks because you left it in radians is the most common trig error.
2. Statistics mode reset. If you enter a data set for Question 5 and forget to clear it before Question 8, the mean/SD tables are wrong. Press SHIFT + CLR + Statistics between questions.
3. Answer memory. The Ans key remembers the previous line — brilliant for iteration (x_n+1 = g(x_n) in IAL P3) but disastrous if you use it after a mistake.
4. Fraction display mode. Set to a/b (proper fraction) unless the question specifies a decimal. Marks are almost always awarded for the exact fraction.
5. Table mode. Use it to graph a function quickly — set start, end, step. Great for sketching before differentiating.

Getting the most out of the fx-CG50

• Colour graphs — set two functions and use G-Solve to find intersections.
• Distribution tables (Normal, Binomial, Poisson) — built into STAT mode.
• Complex numbers, matrices, vectors — all one keypress away.
• Runs on 4 AAA batteries. Bring spares to the exam.