Question

Does crime pay? The FBI Standard Survey of Crimes showed that for about 80% of all property crimes (burglary, larceny, car theft, etc.), the criminals are never found and the case is never solved.† Suppose a neighborhood district in a large city suffers repeated property crimes, not always perpetuated by the same criminals. The police are investigating nine property crime cases in this district.

Answer 1

Answer:

The appropriate answer is "11 crimes".

Step-by-step explanation:

Let,

The number of crimes be "n".

Now,

⇒ $P(solved \ at \ least \ one) = 1-P(solved \ none \ of \ n)$

or,

⇒ $1-(0.8)^n>0.9$

⇒       $(0.8)^n<0.1$

By taking log both sides, we get

⇒ $n>=\frac{log(0.1)}{log(0.8)}$

By putting the values, we get

⇒ $n>=10.31$

      $n=11 \ crimes$