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Topic: Proving a definition of multiplication (wrong) by induction
Replies: 19   Last Post: Feb 8, 2013 2:36 AM

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 Jonathan J. Crabtree Posts: 355 From: Melbourne Australia Registered: 12/19/10
Proving a definition of multiplication (wrong) by induction
Posted: Jan 28, 2013 8:17 PM

Multiplication* an arithmetical operation, defined initially in terms of repeated addition, usually written a × b, a.b, or ab, by which the product of two quantities is calculated: to multiply a by positive integral b is to add a to itself b times.

i.e. ab = a added to itself b times

This definition fails proof by induction.

So what other proofs can be used to prove ab does not equal a added to itself b times?

Thanks
Jonathan Crabtree
P.S. Apart from proof by common sense. Eg.

let a = 1 and b = 0
so 1 x 0 = 1 + 0 (by definition)
and 1 x 0 does not equal 1

or

let a = 1 and b = 1
so 1 x 1 = 1 + 1 (by definition)
and 1 x 1 does not equal 2

* http://www.collinsdictionary.com/dictionary/english/multiplication