Se Pedro é inocente, então Lauro é inocente. Se Roberto é inocente, então Sônia é inocente. Ora, Pedro é culpado ou Sônia é culpada. Segue-se logicamente, portanto, que:

Chama-se tautologia a toda proposição que é sempre verdadeira, independentemente da verdade dos termos que a compõem. Um exemplo de tautologia é:

Três amigos − Luís, Marcos e Nestor − são casados com Teresa, Regina e Sandra (não necessariamente nesta ordem). Perguntados sobre os nomes das respectivas esposas, os três fizeram as seguintes declarações:

Nestor: "Marcos é casado com Teresa"

Luís: "Nestor está mentindo, pois a esposa de Marcos é Regina"

Marcos: "Nestor e Luís mentiram, pois a minha esposa é Sandra"

Sabendo-se que o marido de Sandra mentiu e que o marido de Teresa disse a verdade, segue-se que as esposas de Luís, Marcos e Nestor são, respectivamente:

Um crime foi cometido por uma e apenas uma pessoa de um grupo de cinco suspeitos: Armando, Celso, Edu, Juarez e Tarso. Perguntados sobre quem era o culpado, cada um deles respondeu:

Armando: "Sou inocente"

Celso: "Edu é o culpado"

Edu: "Tarso é o culpado"

Juarez: "Armando disse a verdade"

Tarso: "Celso mentiu"

Sabendo-se que apenas um dos suspeitos mentiu e que todos os outros disseram a verdade, pode-se concluir que o culpado é:

Sabe-se que a ocorrência de B é condição necessária para a ocorrência de C e condição suficiente para a ocorrência de D. Sabe-se, também, que a ocorrência de D é condição necessária e suficiente para a ocorrência de A. Assim, quando C ocorre,

NEW WAYS TO WORK

Six-month long vacations? Factories and offices designed by the employees themselves? These are just a few of the innovations now being tried by business firms in Europe and the United States to combat the increasing dissatisfaction of employees at every level with the quality of their working lives, despite higher salaries, more attractive fringe benefits, and improvements in on-the-job-safety and comfort. In addition to the widely reported boredom of the assembly line, a growing number of white-collar workers see themselves as conscripted into a slave army of paper pushers. Such long-sought benefits as the five-day, forty-hour week, the fixed vacation, and the standard length of service pay raise are no longer enough to compensate many industrial and office workers for the drabness, lack of recognition, impersonality, and apparent pointlessness of their jobs.

(adapted from the book "Words you Need")

NEW WAYS TO WORK

Six-month long vacations? Factories and offices designed by the employees themselves? These are just a few of the innovations now being tried by business firms in Europe and the United States to combat the increasing dissatisfaction of employees at every level with the quality of their working lives, despite higher salaries, more attractive fringe benefits, and improvements in on-the-job-safety and comfort. In addition to the widely reported boredom of the assembly line, a growing number of white-collar workers see themselves as conscripted into a slave army of paper pushers. Such long-sought benefits as the five-day, forty-hour week, the fixed vacation, and the standard length of service pay raise are no longer enough to compensate many industrial and office workers for the drabness, lack of recognition, impersonality, and apparent pointlessness of their jobs.

(adapted from the book "Words you Need")

THE WORLD HEALTH ORGANISATION

Is the body that wiped out smallpox and has done so much to promote mass vaccination losing its way? In recent weeks the reputation of the World Health Organisation (WHO) has suffered a number of blows, as critics have accused it of bowing to political pressures rather than publishing unpalatable research findings.

One instance emerged last week. A controversial new study which looked for links between lung cancer and passive smoking found that non-smokers married to or growing up with smokers were not at significantly more risk from lung cancer than anyone else. The research, commissioned by the WHO and co-ordinated by Rodolfo Saracci of the WHO’s International Agency for Research on Cancer, involved a long study. Since it was one of the biggest single pieces of research conducted into the issue, its results were eagerly awaited by the medical world and lobby groups. But instead of being released with a fanfare, they were summarised in three short paragraphs and buried in a bulky WHO internal document.

(adapted from "The Economist", mar 98)

THE WORLD HEALTH ORGANISATION

Is the body that wiped out smallpox and has done so much to promote mass vaccination losing its way? In recent weeks the reputation of the World Health Organisation (WHO) has suffered a number of blows, as critics have accused it of bowing to political pressures rather than publishing unpalatable research findings.

One instance emerged last week. A controversial new study which looked for links between lung cancer and passive smoking found that non-smokers married to or growing up with smokers were not at significantly more risk from lung cancer than anyone else. The research, commissioned by the WHO and co-ordinated by Rodolfo Saracci of the WHO’s International Agency for Research on Cancer, involved a long study. Since it was one of the biggest single pieces of research conducted into the issue, its results were eagerly awaited by the medical world and lobby groups. But instead of being released with a fanfare, they were summarised in three short paragraphs and buried in a bulky WHO internal document.

(adapted from "The Economist", mar 98)