Answer
65 residents of the United States.
Work Step by Step
The probability that the sample contains at least 10 is the complement of the probability that the sample contains fewer than 10.
$P(fewer~than~10)=1-P(at~least~10)=1-0.99=0.01$
Now, try to guess the value of $n$ using excel:
- $n=60$: "=BINOMDIST(9;60;0.27;TRUE)" $=0,0211\gt0.01$
- $n=61$: "=BINOMDIST(9;61;0.27;TRUE)" $=0,0179\gt0.01$
- $n=62$: "=BINOMDIST(9;62;0.27;TRUE)" $=0,0151\gt0.01$
- $n=63$: "=BINOMDIST(9;63;0.27;TRUE)" $=0,0127\gt0.01$
- $n=64$: "=BINOMDIST(9;64;0.27;TRUE)" $=0,0107\gt0.01$
- $n=65$: "=BINOMDIST(9;65;0.27;TRUE)" $=0,00895\lt0.01$
If $P(fewer~than~10)\lt0.01$, then $P(at~least~10)\gt0.99$
