This calculator solves direct proportions using the classic rule of three. Enter A, B and C to find X in the proportion A:B = C:X. Useful for pricing, quantities, recipes, discounts and everyday calculations.
The rule of three is a method to solve a proportional relationship when three values are known and the fourth is unknown.
Formula: X = (B × C) / A
Example: If 2 kg cost 6, then 5 kg cost X = (6 × 5) / 2 = 15.
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