Indiana Jones and his party need to cross a flimsy rope bridge over a mile-deep gorge. It is so dark that it is impossible to cross the bridge without a flashlight. Furthermore, the bridge is so flimsy that it can only support the weight of two people at once. The party has a single flashlight, which has a weak beam, so that whenever two people cross the bridge they are constrained to walk together, at the speed of the slower person. Indiana Jones can cross the bridge in 5 minutes; his girlfriend can cross it in 10 minutes; his father needs 20 minutes and his father's sidekick needs 25 minutes to cross. Finally, they must all reach the other side within one hour. Is it possible for them to achieve this?

It is widely assumed that people need to engage in intellectual activities such as solving crossword puzzles or mathematics problems in order to maintain mental sharpness as they age. in fact, however, simply talking to other people—that is, participating in social interaction, which engages many mental and perceptual skills—suffices. evidence to this effect comes from a study showing that the more social contact people report, the better their mental skills. which of the following, if true, most seriously weakens the force of the evidence cited? (a) as people grow older, they are often advised to keep exercising their physical and mental capacities in order to maintain or improve them. (b) many medical conditions and treatments that adversely affect a person's mental sharpness also tend to increase that person's social isolation. (c) many people are proficient both in social interactions and in solving mathematical problems. (d) the study did not itself collect data but analyzed data bearing on the issue from prior studies. (e) the tasks evaluating mental sharpness for which data were compiled by the study were more akin to mathematics problems than to conversation.