The length of the ribbon needed to cross from one corner of the rectangle to the other corner is 7 1/2 feet.
The length of the ribbon needed can be determined using the Pythagoras theorem.
The Pythagoras theorem: a² + b² = c²
where
a = length
b = base
c = hypotenuse
√4.5² + 6²
√36 + 20.25 = 7.5 feet
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