A rectangular lawn measures 40 m by 25 m. A gravel path 2.5 m wide is laid all around the lawn, on the outside. What is the area of the path in square metres?

The path adds 2.5 m on BOTH sides of each dimension, so the outer rectangle is 45 m $x$ 30 m = 1350 sq m. The lawn itself is $40\times 25=1000$ sq m, so the path = 1350 - 1000 = 350 sq m. The trap 325 is perimeter $x$ width = $2(40+25)\times 2.5$, which misses the four corner squares; 300 is the answer if the path were laid INSIDE the lawn $(1000-35\times 20)$; 1350 is the outer rectangle with the lawn never subtracted.