Everyday calculations

4.1Add, subtract, multiply and divide#

All four operations work on Y and X and leave the answer in X. Subtraction is Y − X and division is Y ÷ X, so key in the first number first.

Example 4.1

Subtract: 10 − 4

1. Key in 10, ENTER, 4 and press −.

   10ENTER4−

Example 4.2

Divide: 10 ÷ 4

1. Key in 10, ENTER, 4 and press ÷.

   10ENTER4÷

Example 4.3

Multiply and add: 6 × 7 + 8

1. Multiply 6 and 7. Key in 8 (the 42 lifts to Y) and add.

   6ENTER7×8+

4.2Negative numbers: the CHS key#

RPN has no separate "minus sign" key for typing. Use CHS (change sign). Key in the number, then press CHS. While you are typing, CHS changes the sign of the number being typed. After a result, it changes the sign of X.

Example 4.4

Add a negative number

1. Key in 5, press CHS, press ENTER, key in 3 and add.

   5CHSENTER3+

Example 4.5

Change the sign of an answer

1. Add 2 and 3, then press CHS.

   2ENTER3+CHS

To type a negative exponent, press CHS after EEX. See the next section.

4.3Very large and very small numbers: EEX#

Press EEX to type a power of ten. Key in the mantissa, press EEX, then key in the exponent (one or two digits). Press CHS after EEX for a negative exponent. EEX with nothing typed gives 1 as the mantissa, so EEX 3 is 1000.

Example 4.6

Key in 1.5 × 10³ and double it

1. Key in 1.5, press EEX, then 3. ENTER, key in 2 and press ×.

   1.5EEX3ENTER2×

Example 4.7

A very small number

1. Key in 2, EEX, CHS, 5 to get 2 × 10⁻⁵. Switch to SCI 2 to see it.

   2EEXCHS5fSCI82

The calculator holds numbers from about 1 × 10⁻⁹⁹ to 9.999999999 × 10⁹⁹. A larger result becomes 9.999999999 × 10⁹⁹ and flag 9 is set. A smaller one becomes zero.

4.4Percentages and percent change#

g%yˣ (%) finds X percent of Y. Y stays in place, so you can add or subtract the result straight away. gΔ%1/x (Δ%) finds the percent change from Y to X.

Example 4.8

Find 8% of 100

1. Key in 100, ENTER, 8 and press g, %.

   100ENTER8g%yˣ

Example 4.9

Add 15% to 200

1. Key in 200, ENTER, 15, g %. Y still holds 200, so press + to add.

   200ENTER15g%yˣ+

Example 4.10

Percent change from 40 to 50

1. Key in 40, ENTER, 50 and press g, Δ%.

   40ENTER50gΔ%1/x

4.5Reciprocal, square and powers#

1/x gives 1 ÷ X. gx²√x squares X. yˣ raises Y to the power X.

Example 4.11

Reciprocal of 8

1. Key in 8 and press 1/x.

   81/x

Example 4.12

2 to the power 10

1. Key in 2, ENTER, 10 and press yˣ.

   2ENTER10yˣ

4.6Use the last answer again#

The last answer is already in X. Just carry on: key in the next number (the answer lifts to Y) or press a function. To use the number that was in X before the last operation, press gLSTxENTER (LSTx).

Example 4.13

Use an answer in the next step

1. Work out 3 + 4. Then key in 2 and multiply.

   3ENTER4+2×

See also How RPN and the stack work: Bring back the last number with LSTx

4.7The history list#

The app records each finished calculation in the history panel, with a note of the keys you pressed and the result. You can use it to look back at your work. The panel is part of the app, not of the calculator keys, so it does not change the stack. See the history guide for how to reuse an entry.

See also See your past calculations in HistoryReuse an earlier result