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Mathematics 20 Online
OpenStudy (anonymous):

Help!! Find the Lateral Area! (__+__sqrt__) https://media.glynlyon.com/o_geo_2010/8/groupi68.gif

OpenStudy (helder_edwin):

the area of which side?

OpenStudy (helder_edwin):

sorry i meant face not side (i'm not sure what is the proper term in english)

OpenStudy (anonymous):

Of the whole prism

OpenStudy (helder_edwin):

ok. did you notice that the top and the base are rectangle triangles??

OpenStudy (phi):

The lateral area is the sum of the areas of the rectangles that form the faces (other than the bases) of the prism.

OpenStudy (anonymous):

thank you!

OpenStudy (phi):

You can do two of the rectangles easily: you know their width and length

OpenStudy (phi):

the 3rd one is harder. You can use pythagoras to find the 3rd side of the triangle, which is the width of the 3rd face

OpenStudy (phi):

Can you find the areas of the 2 easy faces?

OpenStudy (anonymous):

I know that the sum of all three squares/rectangles is 104 and the c side is 7.21

OpenStudy (phi):

how?

OpenStudy (anonymous):

Well the "unknown" sides are squares. and squares are equal on all four sides soooo. you get the area of the rectangle which is 8*4=32 and 6*6= 36 and 6*6=36. and then when you do pythagorean theorem on the triangle, the long side is 7.21.

OpenStudy (anonymous):

Oh and 32+36+36= 104

OpenStudy (anonymous):

but the are for the triangle is 16. sooo 16+16= 32 and then 104+32= 136

OpenStudy (anonymous):

area*

OpenStudy (phi):

they want the answer in the form (__+__sqrt__) so you are on the right track: 8*4 = 32 for one of the faces looks good but the other face is not 6x6 (it is 6 wide and 8 high) for the 3rd side of the triangle, do not change to a decimal a^2+b^2 = c^2 4^2 +6^2 = c^2 16+36= c^2 52= c^2 c= sqrt(52) you can simplify by factoring 52 into 4*13 c= sqrt(4)*sqrt(13) or c= 2*sqrt(13) now you can find the third face: 8 (the height)* 2*sqrt(13)= 16*sqrt(13) add all three

OpenStudy (phi):

and remember lateral area does not include the 2 bases (the triangles)

OpenStudy (anonymous):

but 128 doesn't fit into the answer.

OpenStudy (anonymous):

so im left with (__+16sqrt13)

OpenStudy (phi):

the area of the 3 sides are: 32, 48, 16sqrt(13) or 80+16*sqrt(13)

OpenStudy (anonymous):

Ohh okay, I added the 3 rectangles Thank you very much for helping!

OpenStudy (phi):

Those are the 3 rectangles. Do you mean the two triangles (top and bottom)? top and bottom add up to 24, so the surface area of the entire prism would be 24+80+16sqrt(13)= 104+16sqrt(13) no 128 in sight anywhere!

OpenStudy (phi):

but the lateral area is just the 3 rectangular sides: 4x8, 6x8, and 2sqrt(13) x 8 which add up to 80+16sqrt(13)

OpenStudy (anonymous):

Long day. and yes if you add 48+48+32.

OpenStudy (anonymous):

I need a break for the day!

OpenStudy (phi):

I don't see how you got the 2nd 48. Hope it makes sense...

OpenStudy (anonymous):

It makes a lotttt more sense now!

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