Question 1150828
One of the legs of a right triangle is twice as long as the other, and the perimeter of the triangle is 28. What is the lengths of all three sides, to three decimal places. 
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Assuming "legs" does not mean the hypotenuse c:
a = shortest leg
c^2 = a^2 + (2a)^2 = 5a^2
c = a*sqrt(5)
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{{{P = a + 2a + a*sqrt(5) = 28}}}
{{{a = 28/(3 + sqrt(5))}}}
You can do the arithmetic