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How to calculate percent change

Δ% gives the percentage change from the number in Y to the number in X.

Problem

A share price rose from $48.20 to $61.75. By what percentage? Then it fell back to $55.00. What was that change?

Keystrokes

  1. 48.2ENTER
    48.20

    The old value.

  2. 61.75Δ%
    28.11

    The percent change to the new value.

  3. 61.75ENTER
    61.75

    The new starting point.

  4. 55Δ%
    −10.93

    The change from there.

Answer

The rise is 28.11% and the fall is −10.93%.

Why it works

Δ% computes (X − Y) ÷ Y × 100. The base is always the number you entered first. That’s why a rise and a fall between the same two prices give different percentages.

Unlike most two-number keys, Δ% leaves the old value in Y, so you can try several new values against the same base.

Questions

How do I find a percentage of a number?

Use the % key. See the guide on percentages.

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