📦 Features Structure and Usage

🔢 Module 1: "What is X% of Y?"

For example, if you want to know what 10% of 150 is:

1. Enter X = 10 in the first input.
2. Enter Y = 150 in the second input.
3. Click the Calculate button.
4. The output will appear in the result area, for example, 15.

Formula used:

result = (percent / 100) * base

🧮 Module 2: "X is what % of Y?"

For example, to find out what percent 15 is of 150:

1. Enter X = 15 (value to compare).
2. Enter Y = 150 (total value).
3. Click Calculate.
4. The result will show, e.g. 10%.

Formula used:

result = (part / whole) * 100

❓ Module 3: "X is Y% of what?"

If you know 1000 is 10% of some value, and want to find that value:

1. Enter X = 1000 (partial value).
2. Enter Y = 10 (percentage).
3. Click Calculate.
4. The result will show the total value, e.g. 10000.

Formula used:

result = (part / percent) * 100

📉 Module 4: "Percentage change from A to B?"

To calculate percentage change between two values (e.g., from 100 to 120):

1. Enter Old value = 100.
2. Enter New value = 120.
3. Click Calculate.
4. The result will be 20% (since it increased by 20 from 100).

Formula used:

result = ((newValue - oldValue) / oldValue) * 100

🕹️ Additional Features

• ⌨️ Keyboard Shortcut: Press Enter to calculate math expressions from the top inputs (using mathjs evaluate function).
• 🧾 History: All calculations are saved in the history panel, including manual and percentage module results.
• 🔁 Undo/Redo: Logic is prepared for undo/redo stacks (not yet active in UI).

🧪 Testing Tips

Try these test inputs for each module:

• Module 1: 25% of 200 → Result: 50
• Module 2: 50 of 200 → Result: 25%
• Module 3: 50 is 25% of what? → Result: 200
• Module 4: from 150 to 180 → Result: 20%