SSC CPO SI and ASI 2011 Paper

Question : 128 of 200

Marks: +1, -0

The base of a solid right prism is a triangle whose sides are 9 cm, 12 cm, and 15 cm. The height of the prism is 5 cm. Then, the total surface area of the prism is

180 cm $^{2 }$
234 cm $^{2 }$
288 cm $^{2 }$
270 cm $^{2 }$

Validate

Solution:

(3) Semi-perimeter of triangle is

{s}= {a+b+c}/{2}= {9+12+15}/{2}=18 {cm}

So, Area of triangle(base) is

√{s(s-a)(s-b)(s-c)}

=√{18(18-9)(18-12)(18-15)}

=54 {cm}^{2}

Now, Total surface area of the Prism = Perimeter of base × height + 2 × area of base
= 36 × 5 + 2 × 54 = 288 cm

^{2}

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