Question 428553
Use the Pythagorean theorem. Let the blanket be retangular or even a square. Choose one side to be a length between 26 and 27 inches. Choose the other sides to be a length also between 26 and 27 inches. You pick.
Then use this formula to find the diagonal
{{{DiagonalInInches = sqrt((LengthInInchesOfFirstSide)^2 + (LengthInInchesofSecondSides)^2)}}}

For example, if you chose both sides to be 26 inches, then the diagonal is
{{{26*sqrt(2)}}} inches