Question

A cone has a slant height of 8 cm and a radius of 2 cm. Estimate the surface area using π =3, and then calculate a more accurate surface area using π =3.14.

Answer 1

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Answer:

• initial estimate: 60 cm²
• better estimate: 62.8 cm²

Explanation:

The total surface area of a cone with radius r and slant height s is ...

A = πr² +πrs = πr(r +s)

For the given dimensions and π≈3, the area is approximately ...

3(2 cm)(2 cm +8 cm) = 60 cm²

For π≈3.14, the area is approximately ...

(20cm²)(3.14) = 62.8 cm²