document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=1062168>Question 1062168</A>: <I><SPAN STYLE=\"word-break: break-all;\"> Hi I have a question that I've been doing over and over again and getting the same different answer than in my textbook and I can't figure out why. The question says to find the surface area of a regular right angle triangular pyramid where you know the sides of the base are 12.9 cm, the distance from the centroid to the to the centre of the base is 5.6 cm, and the slant height is 7.2 cm. When I found the area of the base I did 3(12.9x5.6/2), and got 108.36, and to get the area of the 3 other equal triangles I did 3(12.9x7.2/2), and got 139.32. Then I added these together and got 247.68 cm^2. The answer at the back of my textbook says the answer is 211.4 cm^2. Please tell me where I went wrong and how to fix it. Thank you! </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #676995 by </B><A HREF=/tutors/aboutme.mpl?userid=math_helper><B>math_helper(2461)</B></A><img src=\"/images/stars/stars-13.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=math_helper><IMG SRC=http://www.algebra.com/images/aboutme-small.gif BORDER=0 alt=\"About Me\" VALIGN=MIDDLE></A>&nbsp;<IMG SRC=http://www.algebra.com/cgi-bin/show-face.mpl?user=math_helper><BR>You can <A HREF=\"/cgi-bin/embed-solution.mpl?show=1&solution=676995\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> For the base, I get:  <BR>\n" );
document.write( "    <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=+h+=+sqrt%2812.9%5E2+-+6.45%5E2%29+=+11.17173+ ALIGN=MIDDLE  ALT=\"+h+=+sqrt%2812.9%5E2+-+6.45%5E2%29+=+11.17173+\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "    <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=+A_base+=+%281%2F2%29%28h%29%28b%29+=+%281%2F2%29%2811.17173%29%2812.9%29+=+72.0576+ ALIGN=MIDDLE  ALT=\"+A_base+=+%281%2F2%29%28h%29%28b%29+=+%281%2F2%29%2811.17173%29%2812.9%29+=+72.0576+\"   DISABLED_style= \"max-width:90%; height:auto;\" >  sq in\r<BR>\n" );
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document.write( "—<BR>\n" );
document.write( "For the sides:\r<BR>\n" );
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document.write( " Each face <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=+A_face+=+%281%2F2%29%287.2%29%2812.9%29+=+46.44+ ALIGN=MIDDLE  ALT=\"+A_face+=+%281%2F2%29%287.2%29%2812.9%29+=+46.44+\"   DISABLED_style= \"max-width:90%; height:auto;\" > sq in\r<BR>\n" );
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document.write( "Total Area = 3*A_face + A_base<BR>\n" );
document.write( "                     3*(46.44) + 72.0576  = 139.22 + 72.0576 = 211.3776 sq in\r<BR>\n" );
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document.write( "My answer agrees with your textbook.   The problem appears to be in your calculation of the area of the base.   I recommend drawing the base (equilateral triangle) and figure the height yourself.  The number 5.6cm may just be a distractor thrown in, I didn't use it.\r<BR>\n" );
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