Respuesta :

Answer:

157.98  [tex]in^2[/tex]

Step-by-step explanation:

Given: volume of pyramid is equal to 100 cubic inches and height of the pyramid is 5 inches

To find: surface area of the pyramid

Solution:

Let h denotes the height of the pyramid and 'a' denotes side of the square base of the pyramid.

Volume of the pyramid = [tex]\frac{1}{3}a^2h[/tex]

Also,

Volume of the pyramid = 100 cubic inches

[tex]\frac{1}{3}a^2h=100\\\frac{1}{3}a^2(5)=100\\a^2=\frac{100\times 3}{5}=60\\a=\sqrt{60}[/tex]

Surface area of the pyramid  [tex](S) =a\sqrt{4h^2+a^2}+a^2[/tex]

So,

[tex]S=\sqrt{60}\sqrt{100+60}+60\\=\sqrt{60}\sqrt{160}+60\\=\sqrt{9600}+60\\=97.9796+60\\=157.9796\\\approx 157.98[/tex]

Surface area = 157.98  [tex]in^2[/tex]

Answer:

Surface area of the pyramid = 157.99 in²

Step-by-step explanation:

Volume of a pyramid is given by the formula,

Volume = [tex]\frac{1}{3}(\text{Area of the base})\times \text{height}[/tex]

100 = [tex]\frac{1}{3}\text{(Side)}^{2} \times \text{height}[/tex]

300 = s² × 5

s² = 60

s = √60

s = 2√15 in ≈ 7.746 in

Now surface area of the pyramid = Area of base + 4×(Area of one lateral side)

Area of square base = (Side)² = 60 in

Area of one lateral side = [tex]\frac{1}{2}(\text{Base})(\text{Lateral height})[/tex]

Since Lateral height = [tex]\sqrt{(h)^{2}+(\frac{S}{2})^{2}}[/tex] [By applying Pythagoras theorem in the given triangle]

                                  = [tex]\sqrt{(5)^{2}+(3.873)^{2}}[/tex]

                                  = [tex]\sqrt{25+15}[/tex]

                                  = [tex]\sqrt{40}[/tex]

                                  = 6.325 in.

Now area of lateral side = [tex]\frac{1}{2}(7.746)(6.325)[/tex]

                                        = 24.497 in²

Surface area of the pyramid = 60 + (4×24.497)

                                               = 60 + 97.987

                                               = 157.987 in²

                                               ≈ 157.99 in²

Q&A Education