[Inductive step only] To prove for n=k+1, P(odd number land on butter for (k+1)th toast) = (k+1)/[2(k+1)+1] = (k+1)/(2k+3)
From assumption: P(odd number land on butter for kth toast) = k/(2k+1)
P(odd number land on butter for (k+1)th toast) = k/(2k+1) + 1/(2k+3) * 1/(2k+1)
This is by adding...