An octagonal based pyramid has base side lengths of 20 cm and slant height of 80 cm. What is the surface area?

9514 1404 393

  800(9 +√2) cm² ≈ 8331.4 cm²

Step-by-step explanation:

The surface area of the pyramid is the sum of the areas of the base and triangular faces.

The base area is given by ...

  A = 2(1 +√2)s² . . . . . where s is the length of one side

  A = 2(1 +√2)(20 cm)² = 800(1 +√2) cm²

The lateral area is given by ...

  A = (1/2)Ph . . . . . where P is the perimeter of the base and h is the slant height

  A = (1/2)(8)(20 cm)(80 cm) = 6400 cm²

Then the total surface area of the pyramid is ...

  SA = (800(1 +√2) +6400) cm² = 800(9 +√2) cm² ≈ 8331.4 cm²

area of part 1:

a1=base*height/2=(8+2)*(8-2-2-1)/2=10*3/2=15 ft^2

area of part 2:

a2=length*width=(8+2)*1=10 ft2

area of part 3:

a3=length*width=8*2=16 ft2

total shaded area : a1+a2+a3=41 ft2

total area of the reactangle : a=16*8=128 ft2

total area of the nonshaded region : 128-41=87 ft2

let's solve your equation step-by-step.

4x+2=2x+12

step 1: subtract 2x from both sides.

4x+2−2x=2x+12−2x

2x+2=12

step 2: subtract 2 from both sides.

2x+2−2=12−2

2x=10

step 3: divide both sides by 2.

2x

2

=

10

2

x=5

step-by-step explanation: