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Grade 1010 grade maths

A solid cube whose edges are 12 cm each, has been cut by a plane such that the plane bisects three edges meeting at a corner. the surface area of the remaining part of cube after the small piece is removed is :

A) 81 + 10 root3

B) 810 + 10 root 3

C) 810 - 10 root 3

D) 810 + 18 root3

Profile image of Ashwin
11 Years agoGrade 10
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1 Answer

Profile image of Ravi
11 Years ago
Answer is D
Total SA before dissection.: 6a2= 864 ...(A)
Areaof the faces removed=3(1/2* 6*3)= 54 ...(B)
Area of the new open surface added after dissection to the bigger piece= Area of Equilateral triangle of side 6*21/2= 31/2*(6*21/2)2/4= 18*31/2 ...(C)
New total surface area= A-B+C