Question

example 1
suppose you have a cookie jar containing 5 chocolate chip cookies, 8 snickerdoodles, and 7 oatmeal raisin cookies.
(b) if you randomly select 2 cookies, what is the probability that they are both chocolate chip?
answer: \\( \frac { 5 } { 20 } \cdot \frac { 4 } { 19 } = \frac { 20 } { 380 } \\)
where does the 4/19 come from?
o a there are 4 snickerdoodles out of 19 cookies.
o b the second jar only has 19 cookies.
o c after taking 1 chocolate chip cookie out of the jar, there are only 4 left out of now 19 total cookies.

Explanation:

When calculating the probability of selecting two chocolate - chip cookies, the first selection: there are 5 chocolate - chip cookies out of \(5 + 8+7=20\) total cookies. After taking out one chocolate - chip cookie, for the second selection, there are \(5 - 1 = 4\) chocolate - chip cookies left and the total number of cookies is \(20-1 = 19\). So the probability of the second cookie being chocolate - chip is \(\frac{4}{19}\).

Answer:

C. After taking 1 chocolate chip cookie out of the jar, there are only 4 left out of now 19 total cookies.