Reading scales is something which we tend to take for granted, but they can be much trickier than they first appear. To begin with children will come across scales where every division is labelled, but most scales in real life do not do this. Litre jugs, minutes on a clock, rulers etc often have divisions which are not labelled.
These pages look at a scale drawing of a ruler where only the 10 cm divisions are labelled. One way of understanding this is to think of it as a number line. Start at the nearest marked unit and count forwards or backwards to reach the arrow. This page is most suited to Year 2 children (6/7 yrs old).