Rule of three direct proportion
The rule of three is a method to solve proportions. If we have three numbers: a, b, c, such that, (a / b = c / x), (i.e., a: b :: c: x) we can calculate the unknown value (x).
We have, by the expression: (a : b :: c : x), that the product of the means is equal to the product of the extremes, using the cross-multiplication method, where:
a*x = b*c.
If, a change in the amount causes a change in the unknown amount, at the same proportion, the amounts are in direct proportion.
If, 4 kg of a product have a cost of $36.00, how much would the cost of 18kg? Problem formulation:
4 kg - cost $36.00
18 kg - cost x
By applying the cross products rule on the expression below:
4 / 18 = 36 / x;
So, we have:
x = (18 * 36) / 4 = 162;
x = $162.00
As seen, the increased quantity, resulting in an increased cost.
To fill a 1,000-gallon tank takes two hours. What is the necessary time to fill the tank with 9500 gallons?
1000/ 9500 = 2 / x;
x = (9500 * 2) / 1000 = 19;
x = 19 hours.
How to calculate the Rule of three - direct proportion.
Percent of a number Percent of a total Accumulated total by a percentage Percentage of two numbers Arithmetic mean Geometric mean Harmonic mean Quadratic mean Weighted mean Weighted geometric mean Weighted harmonic mean Standard Deviation Correlation Coefficient Simple Linear Regression Quadratic equation Cubic equation solver Nth root solver Nth Power of a number Logarithm & antilogarithm solver Trigonometric Functions Inverse Trigonometric Functions Directly proportional division Inversely proportional division Determinant matix 3 by 3 Linear equations in two variables Linear equations in three variables Rule of three - Direct proportion Rule of three - Inverse proportion Compound Rule of three Restaurant - checking the bill