What is the surface area of a triangular prism with a length of 8 base of 4 height of 6 and side length of 6.3

The area of the two triangular bases is
  A = (4 mm)(6 mm) = 24 mm²

The perimeter of the triangular base is
  P = 2(6.3 mm) + 4 mm = 16.6 mm
so the lateral area is
  A = (16.6 mm)(8 mm) = 132.8 mm²

The total surface area is the sum of the base areas and the lateral area.
  total area = 24 mm² + 132.8 mm² = 156.8 mm²

This value corresponds to selection ...
  D) 156.8 mm²

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