Calculator Input
Example Data Table
| Case | A | B | C | D | Outcome |
|---|---|---|---|---|---|
| Solve missing denominator | 12 | 4 | 21 | Blank | D = 7 |
| Verify equal proportion | 8 | 2 | 20 | 5 | Balanced proportion |
| Detect mismatch | 9 | 3 | 10 | 4 | Not balanced |
Formula Used
This method works for direct proportions. The calculator either finds the missing term or checks whether both cross products remain equal.
How to Use This Calculator
- Enter values for any three terms in the ratio A / B = C / D.
- Leave one box empty if you want the calculator to solve it.
- Enter all four values if you only want to verify the proportion.
- Choose the decimal precision and tolerance for rounded comparisons.
- Press calculate to view the result, worked steps, and graph above the form.
- Use the CSV or PDF buttons to save the displayed result.
Frequently Asked Questions
1) What does this cross division calculator do?
It solves one missing term in A / B = C / D or verifies whether a completed proportion is balanced using cross products and ratio comparison.
2) Can I enter decimals, fractions, or negative numbers?
You can enter decimals and negative values. This version expects numeric entries in decimal form, so convert written fractions like 3/4 into 0.75 first.
3) Why can’t B or D be zero?
B and D are denominators in the proportion. Division by zero is undefined, so a valid direct proportion cannot use zero in those positions.
4) What happens when I fill all four boxes?
The calculator switches to verification mode. It computes both cross products, compares them, and reports whether the proportion matches within your tolerance.
5) What is the tolerance setting for?
Tolerance handles tiny rounding differences. If the gap between cross products stays within that limit, the result is treated as balanced.
6) Is cross division the same as cross multiplication?
They are closely related here. You first cross multiply to form an equation, then divide to isolate the missing term.
7) When should I increase the decimal precision?
Use higher precision for scientific values, repeating decimals, or close comparisons. It helps reduce visible rounding loss in the final display.
8) What does the chart show?
The Plotly graph displays A, B, C, D, and both cross products. It gives a quick visual check of scale and balance.