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A right prism has a triangular base whose sides are 13 cm, 20 cm and 21 cm. If the altitude of the prism is 9 cm, then its volume is
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- 1314 cm³
- 1134 cm³
- 1413 cm³
- 1143 cm³
- 1314 cm³
Correct Option: B
In ∆ABC, a = 13 cm., b = 20 cm., c = 21 cm., 
| Semi-perimeter = s = | = |  |  | cm. | ||
| 2 | 2 |
| = | = 27 cm. | |
| 2 |
∴ Area of ∆ABC =
∴ Area of the base of prism = √s(s - a)(s - b)(s - c)
= √27(27 - 13)(27 - 20)(27 - 21) = √27 × 14 × 7 × 6
= √3 × 3 × 3 × 2 × 7 × 7 × 2 × 3
= 3 × 3 × 2 × 7 = 1236 sq.cm.
∴ Volume of prism = Area of base × height
= 126 × 9 = 1134 cu.cm.
