Four people crossed it at a time, but 1 needs to be crossed back, which means three people crossed it five times at a time, so the last crossing was 3×5 = 15 people, so there were 5+ 1=6 times.

It is an important goal of mathematics teaching and an important content of mathematics quality education to cultivate students' logical thinking ability through interesting mathematics games. Logical thinking ability is very important at any stage of a person's life.

In the early stage of developing thinking ability in childhood, if we pay attention to cultivating logical thinking ability, then at least the study of mathematics and science will be easier in the future, and in the long run, the depth of analysis and thinking will be different when encountering problems in the future.

In fact, in life, logic is everywhere. Whether we intend it or not, logic is always serving our lives. Many interesting things in daily life.