# SOLUTION: Find the area of an equilateral triangle that has a perimeter of 21 inches. Round the answer to one decimal place.

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 Geometry: Triangles Solvers Lessons Answers archive Quiz In Depth

 Question 318522: Find the area of an equilateral triangle that has a perimeter of 21 inches. Round the answer to one decimal place.Found 3 solutions by Earlsdon, mananth, Fombitz:Answer by Earlsdon(6287)   (Show Source): You can put this solution on YOUR website!You could use Heron/Hero's formula for finding the area of a triangle when you know the lengths of the three sides, a, b, and c. s = the semi-perimeter of the triangle. = = Make the appropriate substitutions: sq.in. (Rounded to one decimal place.) Answer by mananth(12270)   (Show Source): You can put this solution on YOUR website!perimeter of equilateral triangle = 21 side = 7 s=21/2 area = sqrt{s(s-a)(s-b)(s-c)} area=sqrt{21/2(21/2-7)^3} area = 21.2 sq.in Answer by Fombitz(13828)   (Show Source): You can put this solution on YOUR website! . . . . . . Find h using the Pythagorean theorem. . . . Find using the perimeter. Substitute, or approximately, The area is 17.3 sq. inches.