+0  
 
0
55
1
avatar

What’s the surface area of this octagonal prism? I really need help on this!

 

 Apr 19, 2020
 #1
avatar+20808 
+1

I messed up the other answer because I found the volume, not the area.

 

There's a problem with the drawing. If this is a regular octagon and each edge is 2 cm, the diameter will be close to,

but not quite equal to, 4.5 cm.

 

There is a formula for the area of a regular octagon:  Area  = 2 · ( 1 + sqrt(2) ) · (edge)2 

When the edge = 2:      Area  =  2 · ( 1 + sqrt(2) ) · (2)2   =  8 · ( 1 + sqrt(2) )  =  19.314 cm2   (approx)

 

To find the total area, we need two of the regular octagons (38.638 cm2), plus the 8 sides.

Each side has an area of  2 x 6.5 =  13 cm2.

Multiplying this by 8, we get  104 cm2

 

Final amount:  (38.638 cm2) + (104 cm2)  =  142.6 cm2

 Apr 19, 2020
edited by geno3141  Apr 19, 2020

25 Online Users