18. The perimeter is simply √3 + √3 + √3 + √3 or 4√3cm, since the perimeter is just all sides added together. You could add the decimal numbers together using a calculator, which I'm not sure if you're supposed to do in your class.

The area is just width times length, so √3 • √3 = 3cm².

19. The perimeter is 2√5 + 2(9 - √5).

This can also be written as 2√5 + 18 - 2√5, which leaves you with a perimeter of 18ft.

The area would be √5 • (9 - √5), which leaves you with (9√5 - 5)ft².

20. The formula for the perimeter (or circumference) of a circle is π times the diameter of the circle. Using the radius of the circle, 1/π, the diameter is 2/π, so

π • 2/π = 2. The circumference of the circle is 2 inches.

The area of the circle is calculated with the equation πr², so

π(1/π)² = π • 1/(π²) = π/(π²) = π. The area is simply π in².

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3 years ago