[obm-l] 21

To: obm-l@xxxxxxxxxxxxxx
Subject: [obm-l] 21
From: Klaus Ferraz <klausferraz@xxxxxxxxxxxx>
Date: Fri, 27 Jan 2006 17:38:11 +0000 (GMT)
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Como obter o numero 21 usando apenas os numeros 1,5,6,7 ,somente uma vez, e as quatro operacoes matematicas (+, - , * , / )