Problema (nível 2): O David e três dos seus melhores amigos foram jantar a um restaurante. Quando chegaram, sentaram-se numa mesa redonda. Sabemos que: Indica o primeiro nome do Henriques e o prato que ele escolheu para jantar. (image1) o Ferreira estava sentado em frente do amigo que pediu iscas; o apelido do Afonso não é Ferreira; o Afonso sentou-se à esquerda do amigo que pediu massa à bolonhesa; o Gonçalves sentou-se à esquerda do amigo que comeu lulas grelhadas; quem pediu jardineira sentou-se à esquerda do Carlos; o Bernardo estava sentado em frente do Esteves.


Conteúdo referenciado:
[image1]
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Resolução: Vamos analisar as informações dadas, representando num esquema os nomes próprios (Afonso, Bernardo, Carlos e David) por $A,B,C,D$, os apelidos (Esteves, Ferreira, Gonçalves e Henriques) por $E,F,G,H$ e os pratos (iscas, jardineira, lulas e massa) por $I,J,L,M$, respetivamente. Portanto, o primeiro nome do Henriques é Bernardo e ele escolheu jardineira. A disposição completa dos amigos e dos pratos escolhidos está indicada no esquema seguinte. (image2) (image3) (image4) O Ferreira estava sentado em frente do amigo que pediu iscas e o apelido do Afonso não é Ferreira. Temos três possibilidades para o lugar do Afonso: (image5) (image6) (image7) O Afonso sentou-se à esquerda do amigo que pediu massa à bolonhesa. Esta informação exclui a terceira possibilidade, porque nesse caso o Afonso está à esquerda de quem comeu iscas. (image8) (image9) (image10) O Gonçalves sentou-se à esquerda do amigo que comeu lulas grelhadas. Para cada uma das possibilidades, o Gonçalves poderia estar em dois lugares, um dos quais já está ocupado pelo Ferreira. (image11) (image12) (image13) Quem pediu jardineira sentou-se à esquerda do Carlos. Só há um lugar possível para quem comeu jardineira, logo o Carlos comeu iscas. Isto exclui a segunda possibilidade, pois nesse caso, foi o Afonso que comeu iscas. (image14) (image15) (image16) O Bernardo estava sentado em frente do Esteves. Só há um lugar possível para o Bernardo. (image17) (image18) (image19)


Conteúdo referenciado:
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