What ratio is proportional to 18/21

There are many.

Step-by-step explanation:

When you say proportional, you are looking for a ratio that is equivalent to the ratio given. In your case, there are many so you might need to be more specific. But still, we can help you figure it out.

An easy way to do this would be to scale it down to its simplest form and then move upwards. To find proportional ratios, just multiply denominator and the denominator with the same factor.

That is your ratio in its simplest form. Now we can scale up, I'll show you how to do one completely:

That's the same ratio scaled up by a factor of 2.

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That's the ratio given

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Scaled up by a factor of 4

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Scaled up by a factor of 5.

The list goes on and on.