You are very welcome! I looked at this too quickly though. Ignore the above, see below.
So the base is 36. Therefore the area of the square is 36. So if we call each side of the square "S" then S*S = 36 and S = 6. Now we need to find the area of one of the triangles and then multiply that area by 4 and we will have the surface area of the pyramid (without counting the base). So drop the height from the the top of the pyramid straight down to the base and draw a line there connecting to the side of the square (this will be right at the midpoint of the side of the square). That is a right triangle and you can use Pythagorean theorem to find the third side which is the height of our triangle faces. So 10^2 + 3^2 = C^2 109 = C^2 C=109^1/2.
Now find the area: BH/2 6*109^1/2/2 = 3*109^1/2. And multiply that area by 4 because there are four equal triangular faces. 12*109^1/2
Let me know if you have any questions. I know that it can be difficult to visualize without a diagram.
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IMPROVE YOUR READING COMPREHENSION with the ECONOMIST READING COMPREHENSION CHALLENGE:
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2nd set of the Economist Reading Comprehension Challenge: http://gmatclub.com/forum/the-economist-reading-comprehension-challenge-151827.html
3rd set of the Economist Reading Comprehension Challenge: http://gmatclub.com/forum/the-economist-reading-comprehension-challenge-152565.html
4th set of the Economist Reading Comprehension Challenge: http://gmatclub.com/forum/the-economist-reading-comprehension-challenge-156334.html
5th set of the Economist Reading Comprehension Challenge: http://gmatclub.com/forum/economist-reading-comprehension-challenge-156893.html