Suppose the witch weighs W pounds, and the duck weighs D pounds. Also, suppose their average weight is A pounds. (Their combined weight is 2A)
W + D = 2A. (Given)
W = 2A - D. (Subtract D)
W - 2A = -D (Subtract 2A)
W(W - 2A) = W(-D) (Multiply by W)
W(W - 2A) = (2A - D)(-D) (Substitute 2A-D for W using the given equation)
W² - 2AW = -2AD + D² (Distribute)
W² - 2AW + A² = D² - 2AD + A² (Add A²)
(W-A)² = (D-A)². (An expression times itself equals the expression squared)
(W-A) = (D-A) (Square root)
W = D (Add A)
In other words, a witch weighs the same as a duck.
Where did I go wrong?
(In reply to Monty Python logical method
Very Good Larry,
You missed one minor detail though. It happens to be one of my favorites. When the camera first cuts to Sir Bedevere, he is conducting an experiment to see if a swallow can cary a coconut. The poor bird fails, disproving Author's supposed theory.
Another favorite of mine is the line. "A moose once bit my sister."
Did you catch that one?