How do you know that the value of D will decrease when the value of N increases?

Hello! Remember you have to write complete questions in order to find good and exact answers. Here I'll assume that you need a relationship between D and N. So we know some facts:

So this is an inverse relationship. We can write this as:

Since N lies in the denominator, as it increases then D will decrease. So this is a correct relationship

56.6

step-by-step explanation:

the ratio of the perimeters is equal to the scale.

the ratio of the areas is equal to the square of the scale.

34 / 20 = k

a / 19.6 = k²

substituting:

a / 19.6 = (34 / 20)²

a = 19.6 (34 / 20)²

a ≈ 56.6