Flower beds P and Q both have an area of $36{\text{m}}^2$. Each is to be fenced all round at the rate shown. How much more does it cost to fence bed P than bed Q?

Watch for the question wording:

- **Fencing a garden, putting a border, walking around a track** → perimeter (length unit)
- **Painting a wall, covering a floor with tiles, area of cloth needed** → area (square unit)

A classic trap: 'How much wire to fence a square plot of side 20 m?' — perimeter, not area. The wire goes *around* the boundary.