Question

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Answer 1

Question:

A boy makes a cone of diameter 28 cm without a base. He then cuts a smaller cone of diameter 20 cm from the cone. He used the bottom part as a lampshade. If the height of the lampshade is 11cm,

(a) find the volume of the whole cone.

(b) find in cm2, the area of the material used to make the lampshade.

Answer:

(a) V ≈ 16420.1

(b) A ≈ 2690.1 cm²

Step-by-step explanation:

Solution for (a)

Formula: The formula for the volume of a cone is V = 1/3 hπr².

V= πr² h /3 = π × 28/ 2 × 20/  3 ≈ 16420.0576

16420.0576 in nearest tenths is 16420.1

Therefore, the volume of the whole cone is 16420.1 cm²

Solution for (b)

Formula: A = πrl + πr2.

l = r² + h²

Solving for A

A = πr (r + h²+ r²) = π × 20 × (20 + 112 + 202) ≈ 2690.80077

2690.80077 In nearest tenths, is 2690.1

Therefore, the area of the material used to make the lampshade is 2690.1 cm²