Avoids rounding errors - keep full accuracy and only round the final answer.
In short: Storing a value saves a number or result under a variable name so it can be reused exactly in later calculations. On a GDC you press the store key, choose a letter, and recall it by name later. This avoids rounding errors from retyping long decimals and keeps multi-step calculations accurate.
| TI-84 Plus CE | Casio fx-CG50 and fx-CG100 | TI-Nspire CX | |
|---|---|---|---|
| Key sequence | Press STO→ then a letter (e.g. ALPHA, A) to save it; recall the last answer with 2nd → ANS. | Press → (the store key) then ALPHA and a letter to save it. | Type the value then ctrl + var and a name to store it; use ans for the last answer. |
Tip: Rounding too early is one of the most common ways to lose marks - store, don't round.
Tip: Rounding too early is one of the most common ways to lose marks - store, don't round.
Tip: Rounding too early is one of the most common ways to lose marks - store, don't round.
Here's a real IB-style question that uses exactly this technique.
Let x = √50. Without rounding x, find the exact value of 3x².
Avoids rounding errors - keep full accuracy and only round the final answer. An intermediate result has a long decimal, and rounding it early would cost accuracy later. The same value is used in more than one part of a question.
1. Compute a value. 2. Press STO→ then a letter (e.g. ALPHA, A) to save it; recall the last answer with 2nd → ANS. 3. Use the stored letter in later calculations instead of retyping a rounded number.
1. Compute a value. 2. Press → (the store key) then ALPHA and a letter to save it. 3. Use the stored letter in later calculations instead of retyping a rounded number.
1. Compute a value. 2. Type the value then ctrl + var and a name to store it; use ans for the last answer. 3. Use the stored letter in later calculations instead of retyping a rounded number.
Rounding too early is one of the most common ways to lose marks - store, don't round.
In the worked example on this page (2 marks, Paper 2), the marks are: M1: Store √50, then compute 3 × (stored value)²; A1: 150 (exact - rounding x first would have introduced error).
Questions that need this technique link back to this guide. Try one in practice mode, or see every GDC guide.