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The surface area of a balloon varies directly as the
square of mits radius. The area is 325 in? when the
radius is 5 in. What is the area when the radius is
7 in.?


Sagot :

Using a proportional relationship, it is found that the area is of 637 square inches when the radius is of 7 inches.

What is a proportional relationship?

A proportional relationship is a function in which the output variable is given by the input variable multiplied by a constant of proportionality, that is:

[tex]y = kx[/tex]

In which k is the constant of proportionality.

In this problem, the surface area of a balloon varies directly as the square of mits radius, hence:

[tex]S = kr^2[/tex]

The area is 325 in² when the radius is 5 in, hence we use it to find r.

[tex]S = kr^2[/tex]

[tex]325 = 25k[/tex]

[tex]k = 13[/tex]

Hence:

[tex]S = 13r^2[/tex]

When the radius is of r = 7 in, the area in square inches is given by:

[tex]S = 13r^2 = 13 \times 49 = 637[/tex]

More can be learned about proportional relationships at https://brainly.com/question/10424180