Constant of proportionality, step by step

In a proportional table one number turns every x into its y.

The question
x3679y24485672y =x

Write the equation for the table in the form y = kx.

x: 3, 6, 7, 9 y: 24, 48, 56, 72

x3679y24485672
24÷3=8
48÷6=8
y=8x
  1. In a proportional table every y is its x times the SAME number — the constant of proportionality. Find it by dividing a y by its own x.
  2. Take the first column: 24 ÷ 3 = 8.
  3. Check another column so it is not a fluke: 48 ÷ 6 = 8. Every column gives 8, so the constant is 8.
  4. So the equation is y = 8x — it says "each y is x times 8".

How it works.

  1. 01

    In a proportional table every y is its x times the SAME number — the constant of proportionality. Find it by dividing a y by its own x.

  2. 02

    Take the first column: 24 ÷ 3 = 8.

  3. 03

    Check another column so it is not a fluke: 48 ÷ 6 = 8. Every column gives 8, so the constant is 8.

  4. 04

    So the equation is y = 8x — it says "each y is x times 8".