Solution 1: (Equal division method) Because the thermometer is calibrated by equal division method, the actual temperature of each unit of the thermometer can be obtained first, and then multiplied by the number of units that the liquid column rises (or falls) when the thermometer indicates a certain reading, and the actual temperature can be obtained. It can be seen from the problem that when the thermometer shows 4℃, the actual temperature is 0℃; When it shows 99℃, the actual temperature is100℃; Thermometer 99-4=95 represents the actual temperature of 0 ~ 100℃, so the actual temperature represented by each cell is 100/95℃. At 25℃, a * * * is 25-4=2 1, so the actual temperature is t = 22. 1℃.

Solution 2: (Graphic method) Because the scale of the thermometer is uniform, the difference displayed by the thermometer is directly proportional to the difference of the actual temperature. Draw a thermometer according to the meaning of the question, with the actual temperature on the left and the corresponding displayed temperature on the right, as shown in Figure 2-20. Let the actual temperature at 25℃ be t, then (100℃-0℃)/(99℃).

Solution 3: (Mathematical method) Because the thermometer scale is uniform and the temperature change is directly proportional to the height change of the liquid column, the linear function y=kx+b is satisfied.

T = 22. 1℃, which means the actual temperature at 25℃ is 22. 1℃.