1. Bridge crossing problem

There are 5 people crossing the bridge, and there is a torch on the bridge that burns for 30 seconds. The bridge can only pass two people at a time, and they have to send the torch back. The time for these six people to cross the bridge is 6,1,3,12,8 seconds respectively.

The answer

  1. 1, 3 back across the bridge 1; When 4
  2. 1, 6 cross the bridge, 1 come back; 7
  3. 8,12 cross the bridge, 3 come back; When 15

Train of thought

  1. The two that take the most time are the ones that save the most time
  2. The one who comes back the most must be the one who spends the least
  3. There was one trip that took the second least time to get to the least

2. Water pouring problem

There are 3 cups, the capacity is 19L, 13L, 7L; Currently, the 13L and 7L cups are filled with water, while the 19L cup is empty; How do YOU get two 10L cups of water by flipping three cups back and forth?

The answer

  1. 7 liters into 19 liters
  2. 13 liters into 19 liters
  3. 19 liters into 7 liters
  4. 7 liters into 13 liters
  5. 19 liters into 7 liters
  6. 7 liters into 13 liters
  7. 13 liters into 19 liters
  8. 7 liters into 13 liters
  9. 19 liters into 7 liters
  10. 7 liters into 13 liters
  11. 19 liters into 7 liters
  12. 7 liters into 13 liters
  13. 13 liters into 19 liters
  14. 7 liters into 13 liters

Operating rules

  1. Small cup into large cup, medium cup into large cup, then there must be some left over medium cup
  2. Repeat large into small, small into medium, and if medium is full, pour medium into large

Train of thought

  1. If you think about it the other way around, if you want to get two 10s, then the last step is 17,3,0.
  2. So what was his next move? 4,13,3; Sometimes there are several answers in the previous step. Keep in mind that there is a fixed order in which the water is poured, and if the order is out of order, there will be trouble. Order acb)

3. How many mice are needed to test the drug