<PRE><B>Question 974820</B>
I was wrong.  
another way is it is 2.6 x the side length squared.

Area of the first is 625 *2.96=1850
The second is 40% of that or 740
Divide by 2.96=250
Take the square root15.81

The other way is through 6 equilateral triangles.
Area of an equilateral triangle is 
[(sart 3)/4] *a^2, where a is the side.
This is 0.433 a^2.
6 equilateral triangles have 2.598 *a^2.  That is where the 2.6 came from. 

C is the answer.


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