|=0 ‌⇒ad−bc=0 Case I: ad=bc=1 ∴‌‌a=b=c=d=1 Case II: ad=bc=0 a=0,d=0‌‌‌‌‌b=0,c=0 a=0,d=1‌‌‌‌b=0,c=1 a=1,d=0‌‌‌‌‌b=1,c=0 ∴ Total 10 cases when matrix is non invertible Total possible matrix =24=16 Required probability of invertible =‌