Question

kayley needs to find the area of a circle. which process should she use?

she should multiply the diameter by 2 and then multiply the result by 3.14.
she should multiply the radius by 2 and then multiply the result by 3.14.
she should square the diameter and then multiply the result by 3.14.
she should square the radius and then multiply the result by 3.14.

Explanation:

Recall the area formula

The area \(A\) of a circle with radius \(r\) is given by:

$$A = \pi r^2$$

Identify the approximation

The constant \(\pi\) is approximately \(3.14\). Substituting this gives:

$$A \approx 3.14 \cdot r^2$$

Translate to verbal steps

The mathematical expression \(3.14 \cdot r^2\) means:

1. Square the radius (\(r^2\)).
2. Multiply the result by \(3.14\).

Match with options

Let's evaluate the given choices:

• Option 1: Multiply diameter by 2, then by 3.14. (Incorrect)
• Option 2: Multiply radius by 2, then by 3.14. (This calculates circumference, \(2\pi r\))
• Option 3: Square diameter, then by 3.14. (Incorrect)
• Option 4: Square radius, then multiply by 3.14. (Correct)

Answer:

• She should multiply the diameter by 2 and then multiply the result by 3.14.
• She should multiply the radius by 2 and then multiply the result by 3.14.
• She should square the diameter and then multiply the result by 3.14.
• She should square the radius and then multiply the result by 3.14. (Correct answer)