Question 994073
None of the households would be 0.78^20 and your answer is correct.
At least one is the above answer subtracted from 1 or 0.9930.  I used the complement method. At least 1 means not 0.
Exactly 1 is 20(0.22)(0.78^19)=0.0392 as you got.
For 2: 190*(0.22^2)(0.78^18)=0.1050
For 3: 1140(0.22^3)(0.78^17)=0.1777
I get basically the answer you got.