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100 points for $49 worth of Veritas practice GMATs FREE VERITAS PRACTICE GMAT EXAMS Earn 10 Points Per Post Earn 10 Points Per Thanks Earn 10 Points Per Upvote Geometry This topic has 4 member replies Geometry A pyramid with four equal-sized flat surfaces and a base of 36 feet (square) has a height of 10 feet. What is the total surface area of the pyramid, excluding the base? A . 12 root of 31 B. 12 root of 109 C. 24 root of 31 D. 24 root of 109 E. 48 root of 31 Legendary Member Joined 20 Dec 2008 Posted: 540 messages Followed by: 6 members Upvotes: 37 IMO B. from base area, we can calculate the base sides, for a square area36, each side: a=square root of 36=6 Consider the right triangle where, base=6/2=3 and height given=10, then by Pythagoras theorem hypotnuse= square root of (10^2 + 3^2) = square root of 109 now surface area of each side( triangle) = (1/2)*base*height = (1/2)*6*square root of 109 since there are four sides, hence total surface area= 4*(1/2)*6*square root of 109 = Option B _________________ This time no looking back!!! Navami Junior | Next Rank: 30 Posts Joined 22 Aug 2010 Posted: 17 messages Test Date: 22-12-2010 Target GMAT Score: 690 GMAT Score: 320 thank you so much for the reply... But why are we not taking 10 as the height ??? Legendary Member Joined 20 Dec 2008 Posted: 540 messages Followed by: 6 members Upvotes: 37 Pyramid is slant, the height (10) given in the problem is the distance between the pyramid's topmost point to the ground. so to calculate the surface area u need the slant height of each of the triangles (each of the four sides), which can be calculated from Pythagorean theorem. Please Ref to the attached diagram. Attachments This post contains an attachment. You must be logged in to download/view this file. Please login or register as a user. _________________ This time no looking back!!! Navami Junior | Next Rank: 30 Posts Joined 22 Aug 2010 Posted: 17 messages Test Date: 22-12-2010 Target GMAT Score: 690 GMAT Score: 320 thanks a ton! very well explained:-) • Award-winning private GMAT tutoring Register now and save up to$200

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