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Clavis TMUA Set A Paper 2 · Q9

Paper 2Logic & proofNumber & counting

A positive integer is called balanced if and only if it can be written as the sum of two or more consecutive positive integers. For example, 99 is balanced since 9=4+59=4+5, and 1515 is balanced since 15=7+815=7+8.

A (true) theorem states that:

A positive integer is balanced if and only if it is not a power of 22.

So 1,2,4,8,16,…1,2,4,8,16,\ldots are precisely the positive integers that are not balanced.

Which one of the following statements is not true?

AEvery odd number greater than 11 is balanced.
BIf NN is balanced, then 2N2N is balanced.
CIf NN and MM are balanced, then NMNM is balanced.
DIf NN is not balanced, then N+1N+1 is balanced.

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