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Easy

Question

# The area of the slant surface of a cone is 3080 sq. m. If the radius of its base is 28 m, find its height ?

- 22 m
- 21 m
- 31 m
- 41 m

Hint:

### Slant surface of a cone is curved surface

Curved Surface area of cone = πrL

Where L is slant height

L =

## The correct answer is: 21 m

### We have given the cone dimensions

Radius, r = 28 m

Let height of cone be h

We have to find the height of the cone

CSA of cone = 3080 m^{2}

We know that CSA of cone = πrL

h =

Put this value in the CSA formula

3080 = πrL

3080 = x 28 x L

3080 = 22 x 4 x L

3080 = 88 x L

L = 35

Squaring on both sides

1225 = L^{2}

1225 = )^{2}

1225 = h^{2 }+ 784

h^{2}= 441

h = 21 m

Therefore, correct option is b) 21 m

Put this value in the CSA formula

Squaring on both sides

^{2}

^{2}

^{2 }+ 784

^{2}= 441

Therefore, correct option is b) 21 m

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