The probability of dust landing on the carpet is the area of the carpet divided by the area of the room, and the probability of landing in the room but not the carpet is 1-P(C)
P(R!C)=1-P(C)
P(R!C)=1-(((π32^2)/4)/(300*500))
P(R!C)=1-16π/9375
P(R!C)=(9375-16π)/9375
P(R!C)≈0.994638
P(R!C)≈99.5% (to nearest tenth of a percent)