Why Olivia said her pencil is 14.0 cm long how do you know she measured to the nearest millimetre?

Answer 1

You do not, but in the world of science publication, if it was something key, you would have to prove it. Such as saying you made a compound, you have to produce all the spectra. In this case, as it is stated as 14.0cm, it is likely she did not round up. You round up to get rid of figures, not to replace the significant figure with a zero. If she quoted as 14cm, there would be more suspicion.