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Direct Proportion Constant & Values
Find the constant k in y = kx, or recover a compatible value for a relationship through the origin.
- Formula & worked example
- Private in your browser
- No signup
Calculator inputs
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How to use this calculator
- Enter the known values in the units shown. Results update as you type.
- Where results are editable, change one to solve backwards. Lock a value to hold it fixed.
- Use the worked example to check the method. Reset restores the starting fields.
Private by default
Inputs and results stay in this browser tab. Bookify does not upload or store the values you enter.
Formula and method
When x = 4 and y = 12, the direct-proportion constant is k = 12/4 = 3.
y = kx; k = y/x for nonzero x
Worked example
Enter these known values and leave the other values blank.
- Independent value x, nonzero
- 4
- Dependent value y
- 12
- Direct-proportion constant k
- 3
Assumptions and limitations
- This model assumes a straight-line relationship through the origin, with no additive intercept. Enter x other than zero.
- Values and the constant may be signed. If x and y have units, k has units of y divided by units of x; keep those units consistent.
- One pair determines a ratio but does not establish proportionality across a dataset. When k and y are both zero, x is not uniquely recoverable.
Common questions
Is k the slope of any straight line?
Only a line through the origin has y = kx. A line with a nonzero intercept needs an additional parameter.
Can the constant be negative?
Yes. With nonzero x, opposite signs of x and y give a negative constant.
References
The calculation equations, inverse formulas, units, and input rules were imported from this source. Bookify provides the interface and equation solver.
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