To find the hypotenuse \( c \) of a right-angled triangle using the Pythagorean Theorem, the correct formula is:
\[ c = \sqrt{a^2 + b^2} \]
where \( a \) and \( b \) are the lengths of the legs of the triangle. In this case, the legs are 9 inches and 12 inches.
Calculating this step by step:
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Calculate \( a^2 \): \[ 9^2 = 81 \]
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Calculate \( b^2 \): \[ 12^2 = 144 \]
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Add the squares: \[ 81 + 144 = 225 \]
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Take the square root: \[ c = \sqrt{225} = 15 \text{ inches} \]
Since Rosanna calculated \( c \) to be 225 inches, she likely squared the sum instead of taking the square root. Therefore, the correct response would be:
Rosanna should take the square root of the sum when using the Pythagorean Theorem.