"How many times do you need to test?"
"Divide 27 people into 3 groups on average, with 9 people in each group. As a unit, we only need to test it three times to determine which group is infected. In this case, the number of suspicious people will be directly reduced from 27 to 9. Then the infected person is determined by a single test, and only 3+9= 12 tests are needed in total. Is it faster and more efficient than the original detection of 27 times? "
However, students can continue to ask questions. For example, can the nine people in the second round continue to use the grouping method? In fact, we will continue to divide into three groups, each with three people, and then conduct a single inspection in the third round. The number of inspections only needs 3+3+3=9 times, and the number of times is even less. However, if an infected person is found in reality, it needs to be diagnosed at the first time, and the second round of single inspection is faster than continuing to group. At this time, the second round of direct single inspection is more in line with the actual needs of epidemic prevention.
Therefore, mathematical knowledge is closely related to real life.