## probability point selected on segment is within 2 units of 8

Sequences, counting (including probability), logic and truth tables, algorithms, number theory, set theory, etc.
ccav
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Joined: Tue Mar 09, 2010 3:30 pm
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### probability point selected on segment is within 2 units of 8

On a number line from -6 to 14, a point between -6 and 14 will be selected at random. What is the probability that the point selected will be within 2 units of the point at coordinate 8?

I thought within 2 units meant that the point would be from 6 to 10, which are 5 points out of 20 points.

I got an answer of 1/4, but this is apparently wrong. The answer is supposed to be 1/5. I'm stuck here.

king&i
Posts: 23
Joined: Sat Mar 07, 2009 5:13 pm

### Re: probability point selected on segment is within 2 units of 8

How did you get a distance of five units between 6 and 10?

What is the length of the whole line? What is the length that you want to hit? Divide the first by the second.

CHTMcougarette09
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Joined: Wed Mar 24, 2010 7:13 pm
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### Re: probability point selected on segment is within 2 units of 8

You started out correctly by finding the length of the line which is a total of 20 possible points.

Next, the question states what is the probability that the point selected with be within 2 units of 8. This will mean that the points allowed to the left of 8 on the number line is 6 and 7 which equals two points. The points allowed to the left of 8 would be 9 and 10 which equals two points. You do not include the coordinate 8, you are finding within two units of 8.

You will see that you have the options of 6,7, 9 and 10. This will give you a possibility of 4 points to select out of 20 possible point. 4/20 = 1/5

Hope that helped.