Teaching one thing the better to teach another

Significant figures is a confusing concept for most pupils. This is simply because they have been taught to ignore all the leading and trailing zeros in the numbers they write. Because these are not even seen, pupils are not aware of their presence, and ironically, when they are asked to ignore them, they become confused. The solution is to talk about the leading and trailing zeros early on. If one refers the number 100 as "0000100… but we ignore the leading zeros" and talk that talk, then quite quickly pupils will become fed up with you wasting their time by always talking about the leading zeros which we are destined to forget about. Similarly if one refers to 0.21 as "0.210000… but we are going to ignore all the trailing zeros", again pupils will quickly become familiar with the concept of trailing zeros which we ignore. Then, when we start speaking of significant figures, the pupils will be familiar with the concept of insignificant figures (they’ll have had them up to their eyebrows) and they won’t struggle.