# Math Help - Please help me figure this out

I was wondering if this makes sense:

If 45/1000 people commit violent crimes each year... could I multiply that by the average life expectancy and get the chance of each person committing a violent crime in their life time? If not, is there anyway to get that figure from the 45/1000 number?

Thanks for your help!~

HeyBigManOnCampus.

Are the probabilities independent for each year? (Hint: Consider P(Commit Year 1 OR Commit Year 2 OR .... OR Commit Year N)).

Hello, BMOC!

I was wondering if this makes sense:

If 45/1000 people commit violent crimes each year, could I multiply that by the average life expectancy
and get the chance of each person committing a violent crime in their life time?
If not, is there anyway to get that figure from the 45/1000 number?

No, your method does not make sense.

You say 4.5% of the people commit a violent crime each year.
Then someone who is 23 years old has a probability of:
. . $23 \times 4.5\% \,=\,103.5\%$ of committing a violent crime at some time.

The set up is not realistic.

Say, 1000 people (including you) draw numbers from a hat
. . and a certain 45 of them must commit a violent crime.

The probability that you do not commit a crime that year is 95.5%.

Suppose you enter this "lottery" every year.
How likely are you commit a crime?

The probability that you do not commit a crime for 35 years
. . is:. $(0.955)^{30} \:=\:0.199580454 \:\approx\:20\%$

Therefore, the probability that you do commit a violent crime
. . at least once during your first 35 years is $80\%.$

Ha!