16. If [tex]P[/tex] varies inversely as [tex]V[/tex] and [tex]V[/tex] varies directly as [tex]R^2[/tex], find the relationship between [tex]P[/tex] and [tex]R[/tex] given that [tex]R=7[/tex] when [tex]P=2[/tex].

A. [tex]P=98 R^2[/tex]
B. [tex]P R^2=98[/tex]
C. [tex]P^2 R=89[/tex]
D. [tex]P=\frac{R^2}{98}[/tex]



Answer :

Sure, let's solve this step by step!

Given that [tex]\(P\)[/tex] varies inversely as [tex]\(V\)[/tex], we can express this as:
[tex]\[ P = \frac{k_1}{V} \][/tex]
where [tex]\(k_1\)[/tex] is a constant.

Additionally, [tex]\(V\)[/tex] varies directly as [tex]\(R^2\)[/tex], which gives us:
[tex]\[ V = k_2 R^2 \][/tex]
where [tex]\(k_2\)[/tex] is another constant.

To find the relationship between [tex]\(P\)[/tex] and [tex]\(R\)[/tex], we can combine these two relationships. Substituting [tex]\(V\)[/tex] from the second equation into the first equation, we get:
[tex]\[ P = \frac{k_1}{k_2 R^2} \][/tex]

This can be simplified to:
[tex]\[ P = \frac{k}{R^2} \][/tex]
where [tex]\(k = \frac{k_1}{k_2}\)[/tex] is a constant.

We are given the specific values [tex]\(P = 2\)[/tex] when [tex]\(R = 7\)[/tex]. We can use these to determine the constant [tex]\(k\)[/tex]:
[tex]\[ 2 = \frac{k}{7^2} \][/tex]
[tex]\[ 2 = \frac{k}{49} \][/tex]
[tex]\[ k = 2 \times 49 \][/tex]
[tex]\[ k = 98 \][/tex]

So, the relationship between [tex]\(P\)[/tex] and [tex]\(R\)[/tex] can be written as:
[tex]\[ P = \frac{98}{R^2} \][/tex]

Now, let's express this equation in the form given in the multiple choices. The equivalent form is:
[tex]\[ P R^2 = 98 \][/tex]

Thus, the correct relationship between [tex]\(P\)[/tex] and [tex]\(R\)[/tex] is:
[tex]\[ \boxed{P R^2 = 98} \][/tex]

Answer: B. [tex]\(P R^2 = 98\)[/tex].