A rectangular field measures 20 m by 15 m and contains a square flower bed of side 6 m. A ball thrown high lands at a random point of the field. What is the probability that it lands outside the flower bed?

Area of the field = $20\times 15=300{\text{m}}^2$ and area of the bed = $6\times 6=36{\text{m}}^2$, so the favourable area is $300-36=264{\text{m}}^2$ and the probability is 264/300 = 22/25. Answering 36/300 = 3/25 gives the chance of landing ON the bed — the forgotten complement — while 12/35 comes from comparing the perimeters 24 m and 70 m, which is not a valid measure for a randomly placed point.