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A right circular conical structure stands on a circular base of 21 metre diameter and is 14 metre in height. The total cost of colour washing for its curved surface at Rs. 6 per square metre is (Take π = 22/7)
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- Rs. 4365
- Rs. 4465
- Rs. 3465
- Rs. 3365
- Rs. 4365
Correct Option: C
| AC = | metres | |
| 2 |
OC = 14 metre
∴ Slant height (l) = √AC² + CO²
| = √ |  | ² |  | + (14)² | |
| 2 |
| = √ | + 196 | |
| 4 |
| = √ | = √ | ||
| 4 | 4 |
| = | metre | |
| 2 |
∴ Curved surface area = πrl
| = | | × | × | | sq. metre | |||
| 7 | 2 | 2 |
= 577.5 sq. metre
∴ Total expenditure on painting = Rs. (577.5 × 6) = Rs. 3465
