The IB calculator guide: every exam skill on the TI-Nspire, the Casio and the TI-84.

Three mistakes that cost more marks than any formula

1. The argument order. Casio asks for σ before μ; Texas Instruments asks for μ before σ. A student who switches calculator in the last year of school gets plausible wrong answers for weeks.
   Casio NormCD(lower, upper, σ, μ)TI normCdf(lower, upper, μ, σ)
2. The tail. "The tallest 5%" is an area of 0.05 on the right, which is 0.95 on the left. The Casio and the TI-84 have a tail setting; the TI-Nspire does not and always wants the left area. Draw the curve first.
3. The boundary of a binomial. "At least 5" is $P(X \ge 5) = 1 - P(X \le 4)$. Not $1 - P(X \le 5)$. One number off, one mark gone, and the follow-through marks with it.

Which calculators the IB allows

• TI-Nspire CX II (Texas Instruments). Allowed in IB exams. The CX II CAS model is only allowed with CAS disabled in Press-to-Test mode, which your school sets up before the exam. If you have the CAS model, make sure the Press-to-Test light is on before you start.
• Casio fx-CG50 (Casio). Allowed in IB exams. Exam mode (SHIFT, MENU, F3 and F4) is required by some schools: it clears memory and turns the border green for the invigilator.
• TI-84 Plus CE (Texas Instruments). Allowed in IB exams, including the Python edition. Apps that are not on the IB list may need to be removed by your school before the exam, and some schools reset the memory on the day.

Also permitted: NumWorks and the HP Prime in exam mode. Not permitted: any CAS model with CAS active, any device with internet, and ordinary scientific calculators on Maths papers that say "GDC required". The authoritative list is the IB document "Use of calculators in examinations" for the current year, which your IB coordinator has.

Questions students ask

Which calculators are allowed in IB Maths exams?

Graphic display calculators without CAS, or with CAS disabled in exam mode. The three most common are the TI-Nspire CX II (the CAS version only in Press-to-Test with CAS off), the Casio fx-CG50 and the TI-84 Plus CE. NumWorks and the HP Prime (in exam mode) are also permitted. Your school tells you which model it supports; the keystrokes here cover the three you will see in almost every IB classroom.

Which papers allow a calculator?

Maths AA: Paper 1 is without calculator, Paper 2 and HL Paper 3 require one. Maths AI: every paper requires a GDC. Physics: a calculator is allowed on every paper.

Does the IB accept a calculator answer without working?

For a direct computation yes, if you write the mathematical notation (for example P(X > 180) = 0.106) and the answer to the right accuracy. For solving equations the mark scheme usually expects a sketch or the equation set to zero. The write-up section of each guide shows what to put on the paper.

Which calculator should I buy for the IB?

The one your teacher uses, because that is the one you will be shown in class. If you have a free choice, the TI-Nspire CX II and the Casio fx-CG50 both take two bounds in their cumulative distribution commands and both have a clear menu system; the TI-84 Plus CE is older but widely known and cheaper second hand.

Written by Pietro Meloni, PhD, IB Mathematics and Physics tutor, from teaching these procedures one to one. Keystrokes checked on TI-Nspire CX II OS 6, Casio fx-CG50 OS 3 and TI-84 Plus CE OS 5. Not affiliated with the International Baccalaureate Organization, Texas Instruments or Casio; product names are used to describe the products. Found a key that has moved? Write to pietro@pietromeloni.com.