Question

Find the surface area of the cone. Use 3.14 for it.

The surface area is about in.2.
look at the picture ⬇️⬇️⬇️

Answer 1

Answer: 1570 square inches

This value is approximate since pi = 3.14 is approximate.

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Work Shown:

r = radius = diameter/2 = 20/2 = 10 inches

L = slant height = 40 inches

SA = surface area of the cone

`\text{SA} = \pi*r^2 + \pi*r*L\\\\\text{SA} = \pi*10^2 + \pi*10*40\\\\\text{SA} = \pi*100 + \pi*400\\\\\text{SA} = 100\pi + 400\pi\\\\\text{SA} = (100+400)\pi\\\\\text{SA} = 500\pi \text{ ... exact surface area in terms of pi}\\\\\text{SA} \approx 500*3.14\\\\\text{SA} \approx 1570\\\\`

The surface area of the cone is approximately 1570 square inches.

We can abbreviate "square inches" into
`\text{in}^2`

If you want to get a more accurate surface area value, then use more decimal digits of pi.