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Constant of proportionality through (5, 2)

Step by step, with the reason for every step · Proportional relationships · Foundations

Step by step

The question

Question: find the constant of proportionality for the point (5, 2).

(5, 2)

Proportional means: y divided by x is always the same number.

We call that number k.

Then y = k times x.

proportional: y ÷ x is always the same
k = y ÷ x, y = kx

1 Divide y by x

x is 5 and y is 2.

So k is 2/5, which is 0.4.

= k = 25 = 0.4

2 Write the equation

y = k x, with k = 0.4.

So the equation is y = 0.4x.

= y = 0.4x

3 Check

Let's check: k times x should give each y.

0.4 times 5 is 2.

So the answer is right!

0.4 × 5 = 2

Let's look back.

First: divide y by x.

Then: write the equation.

Last: check.

Answer
= y = 0.4x

Your turn

Try this one yourself, then check:

Find the constant of proportionality for the point (5, 3)
Show the answer
k = 0.6, y = 0.6x

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