+0  
 
+1
45
9
avatar

        

          

Hi,

Sorry. I am having a very difficult time with surface area. I tried to work the last two out but I am not sure if they are correct or not*. The other three I can't seem to figure out at all. Please help! Thank you!

 

*(sorry for my crappy writing)

Guest Aug 29, 2018
 #1
avatar+3011 
+2

Last one: There are 6 faces, I think, wait, yes! So, the area of the first face, 2nd face: 2(20*10)=2(200)=400yd^2

Area of the 3rd face, 4th face: 2(20*20)=2(400)=800yd^2

Ares of the 5th face, and 6th face: 2(20*10)=2*200=400yd^2.

 

Thus, the surafce area is 400+400+800=1600yd^2. You're correct!

tertre  Aug 29, 2018
 #2
avatar+3011 
+2

5th one: Two trapezoids! No! Area of a trapezoid: 2(51.85)- use the formula=103.7 mi^2.

Rectangles: 2(14*7)=196 mi^2

Bottom rectangle: 5*14=70 mi^2

Top rectangle: 168 mi^2

So, 103.7+196+70+168=537.7? I might be wrong.

tertre  Aug 29, 2018
 #6
avatar+88830 
0

You are correct,  tertre !!

 

 

cool cool cool

CPhill  Aug 29, 2018
 #3
avatar+3011 
+2

1st one: Base, which is a rectangle: 18*20=360mi^2

2*(1/2*20*14.2) and 2*(1/2*18*14.9)=20*14.2+18*14.9=284+268.2=552.2mi^2

So, 360mi^2+552.2mi^2=912.2mi^2.

tertre  Aug 29, 2018
 #4
avatar
+2

Thank you so much!! I've been having a difficult time with these and I appreciate your help!

Guest Aug 29, 2018
 #5
avatar+3011 
+1

No problem! I am always happy to help!

tertre  Aug 29, 2018
 #7
avatar+88830 
0

Nice job,  tertre.....!!!

 

 

cool cool cool

CPhill  Aug 29, 2018
 #8
avatar+88830 
+1

Third one  (on top right)

 

We have a  triangular  pyramid

 

The sides are 3 congruent triangles  with bases of 9 cm  and heights of 19.2 cm

So...their  total area  is  (3)(1/2) (9) (19.2)   = 259.2 cm^2

 

The base is a triangle with a base  of  9cm  and a height of 7.8 cm

Its  area is  (1/2) (9)(7.8)  = 35.1 cm^2

 

So.....the total surface area  is   259.2  + 35.1   =  294.3 cm^2

 

 

 

cool cool cool

CPhill  Aug 29, 2018
 #9
avatar+88830 
+1

Middle one at top

 

We have a triangular prism

 

The  top/bottom are congruent triangles  with base = 15 in  and height of 7.7 in

So the total area of top/bottom  is    15  * 7.7  = 115.5 in^2

 

The sides are rectangles with height  of  8 in and widths of  ( 15,15 and 8  in)

So the side area  is     8 [ 15 + 15 + 8 ]  = 8 [ 38  ] =  304 in^2

 

So..the total surface area is   115.5  + 304  =  419.5 in^2

 

 

cool cool cool

CPhill  Aug 29, 2018

29 Online Users

New Privacy Policy

We use cookies to personalise content and advertisements and to analyse access to our website. Furthermore, our partners for online advertising receive information about your use of our website.
For more information: our cookie policy and privacy policy.