Posted by **Cindy** on Friday, April 13, 2007 at 5:42pm.

A pentagon is formed by putting together three identical equilateral triangles and one larger equilateral triangle with length of edge equal to 2 times that of the smaller equilateral triangle. If the perimeter of the smaller triangle is 42 cm, what is the perimeter of the pentagon?

i need help setting up an equation for this problem

let each side of the smaller triangles be x

then the length of the larger triangle is 2x

place 2 of the smaller triangles along a side of the larger, the third of the smaller fits between the two other small ones.

"If the perimeter of the smaller triangle is 42 cm" -----> 3x=42 so

x=14

now "walk" around the perimeter of the pentagon, I see x+x+x+2x+2x

do you follow that?

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