A rectangular prism has sides that are in the ratio of 3:5:9. If the volume of the prism is 8640 cm3, then the surface area of the prism, in square millimetres, is_______?

Respuesta :

The surface area of the rectangular prism is 278400 square millimeters, if a rectangular prism has sides that are in the ratio of 3:5:9 and the volume of the prism is 8640 cubic centimeters.

Step-by-step explanation:

The given is,

                Volume of Rectangular prism - 8640 Cubic centimeters

                Ratio of rectangular prism sides are 3:5:9

Step:1

               Formula for volume of rectangular prism,

                                           [tex]Volume, V = whl[/tex]...................................(1)

               Where, w - width of the prism

                            h - Height of the prism

                             l - Length of the prism

               Let, x - side of the rectangular prism

               From given values,

                       Volume, V = 8640 cubic centimeters

                          Width, w = [tex]\frac{3}{17}x[/tex]

                         Height, h = [tex]\frac{5}{17} x[/tex]

                          Length, l = [tex]\frac{9}{17}x[/tex]

              Equation (1) becomes,

                                [tex]8640=(\frac{3}{17}x)(\frac{5}{17} x)(\frac{9}{17}x)[/tex]

                                        [tex]= 0.027478 x^{3}[/tex]

                                    [tex]x^{3}= \frac{8640}{0.027478}[/tex]

                                      [tex]x = \sqrt[3]{314432}[/tex]

                                         [tex]= 68[/tex]

Step:2

              Width, w = [tex]\frac{3}{17}x[/tex]  [tex]= (\frac{3}{17}) (68)[/tex]  [tex]= 12 cm[/tex]

             Height, h [tex]= (\frac{5}{17} )(68) = 20 cm[/tex]

              Length, l [tex]= (\frac{9}{17})(68)=36cm[/tex]

Step:3

            Formula for surface area of rectangular prim,

                                            [tex]A= 2(wl+lh+hlw)[/tex]

            From the values of w, l and h,

                                               [tex]= 2 [(12)(20)+(36)(20)+(36)(12)][/tex]      

                                               [tex]= 2 (240+720+432)[/tex]

                                               [tex]= 2(1392)[/tex]

                                               = 2784 Square centimeters

                                               = 2784 × 100 square millimeters

                         ( 1 square centimeters = 100 square millimeters )

                                            A = 278400 square millimeters

Result:    

             The surface area of the rectangular prism is 278400 square millimeters, if a rectangular prism has sides that are in the ratio of 3:5:9 and the volume of the prism is 8640 cubic centimeters.