Monday

September 22, 2014

September 22, 2014

Posted by **joe** on Thursday, December 18, 2008 at 12:22am.

Suppose you are asked to choose a whole number between 1 and 13 inclusive.

(a) what is the probability that it is odd?...7/13

(b) What is the probability that it is even?...6/13

(c) what is the probability that it is a multiple of 3?...4/13

(d) what i the probability that it is odd or a multiple of 3?.. This is where i am stumped. the book says the answer is 9/13 but i cant find it.

- math probability -
**Reiny**, Thursday, December 18, 2008 at 8:29amthe first 3 are correct

for d)

the odds are 1,3,5,7,9,11,13

multiples of 3 are 3,6,9,12

now the numbers which are either odd OR a multiple of 3 are 1,3,5,6,7,9,11,12,13

or nine of them

so prob = 9/13

There is a formula which says

Prob(A or B) = Prob(A) + Prob(B) - Prob(A and B)

= 4 + 7 - 2 = 9

notice that the 3 and 9 are in both sets, so if we just add up the count, we counted them twice, so we have to subtract one of the counts.

**Answer this Question**

**Related Questions**

Math - Choose a natural number between 1 and 100, inclusive. What is the ...

algebra - Choose a natural number between 1 and 100, inclusive. What is the ...

Probability - A nickel is flipped and a dime is flipped. 1. What is the ...

Math - A nickel is flipped and a dime is flipped. 1. What is the probability of...

probability - please help! 1.) A random digit from 1 to 9 (inclusive) is chosen...

statistics - Suppose that 50 identical batteries are being tested. After 8 ...

math - choose a natural between 1 and 20 inclusive. what is the probability that...

statistics - 50 question multiple choices with A, B, C, D Probability of an ...

statistics - The below table shows the probabilities generated by rolling one ...

Probability - A loaded die has the property that the probability of throwing an ...