Number line
Imagine that you tilt the thermometer and put everything away except its scala.
Then you would get something like below, where the two points A and B represent the values of two seperate thermometers.
Tasks:
1) Calculate the difference between the two values on the scala of A and B.
2) Tick the box "Show arrow" and try to find out, what the red arrow exactly means.
3) Tick the box "Show calculation" to see the background calculation.