`text(Solution 1:)`

`text(One example of the dimensions of a 5250 cm²)`

`text(rectangle can be:  525 cm × 10 cm)`

`text(Converting to millimetres:)`

`5250\ text(mm) xx 100\ text(mm) = 525\ 000\ text(square millimetres)`

`text(Solution 2:)`

`text(Scale factor of converting cm to mm = 10)`

`text(Scale factor of converting cm² to mm²)\ = 10 xx 10 = 100`

`:. 5250\ text(cm²) xx 100 = 525\ 000\ text(mm²)`