Question

Find the area of a circle if i) radius is 21cm ") diameter is 28cm
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Answer 1

Before multiplying by pi. 441π cm²

After multiplying by pi. 1384.74 cm²

Explanation:

The formula for area of a circle is πr².

r=radius

Square the radius.

21²=441

If they want the answer in this form: 441π cm². If not, then use 3.14 for π.

441*3.14=1384.74

The answer is 1384.74 cm².

Hope this helps!

Answer 2

i) 441π cm² ≈ 1385.4 cm²

ii) 196π cm² ≈ 615.8 cm²

Explanation:

The areas of circles with radius 21 cm or diameter 28 cm can be found using the appropriate area formula.

i)

The formula for the area of a circle based on its radius is ...

A = πr²

When the radius is 21 cm, the area is ...

A = π(21 cm)² = 441π cm² ≈ 1385.4 cm²

ii)

The formula for the area of a circle based on its diameter is ...

A = (π/4)d²

When the diameter is 28 cm, the area is ...

A = (π/4)(28 cm)² = 196π cm² ≈ 615.8 cm²