In addition to direct variation, there are relationships that are direct square and direct cube variations.

Do you remember the formula for finding the area of a circle?

The area of a circle is found by multiplying the number pi, π, by the square of the radius, r, of that circle. In other words, A = πr². This formula is an example of a direct square variation where the constant of variation is π.

If the area of a circular garden is about 133 square feet, on your own paper approximate the radius of the garden to the nearest tenth of a foot.

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Check Your Answer

A = πr²

133 = πr²

one-hundred thirty-three over pi 133 π = r²

6.506 ≈ r

The radius of the circular garden is approximately 6.5 feet.