Question

Think you can help me?

Answer 1

I have 4 quarters, 7 nickels, and 2 pennies in my wallet. I take them out of my wallet one at a time at random and don't put them back. What is the probability that the fourth coin I pull out is a nickel and the seventh is a quarter?

Answer 2

Am I suppose to give you the percentage chance of pulling out one?

Answer 3

Or like a fraction?

Answer 4

I would say 2/3

Answer 5

@Loopki40 How did you get 2/3? Just wondering.

Answer 6

A fraction. @Loopki40 Think you can explain how you got the answer?

Answer 7

Since you are putting everything back, why would the sequence of drawing change anything? The events are independent.

p(pulling a nickle) = ??
p(pulling a quarter) = ??

Answer 8

I'm actually not putting everything back ^^;

Answer 9

@amonaroll32

What I'm wondering is what happens if you pull four consecutive quarters on the first four removals from the wallet? Then, the probability would be zero because without replacement, there would be no quarter to select on the 7th pull.

Answer 10

Honestly im not even surehow I got 2/3rds I have to rework it out

Answer 11

@Loopki40 Please do. It would help others in structuring their thinking.

Answer 12

But Directrix I do see what you mean on what if you pulled 4 sonsecutive quaters

Answer 13

You're not supposed to over think it, if that helps. The homework is just a page of trick questions >.<

Answer 14

so its not any multiple choice to it?

Answer 15

Did id say "don't" before? I must have slept through that word.

Draw 1

Q4N7P2

Draw 2

Q(Q3N7P2)
N(Q4N6P2)
P(Q4N7P1)

Draw 3

QQ(Q2N7P2)
QN(Q3N6P2)
QP(Q3N7P1)
NQ(Q3N6P2)
NN(Q4N5P2)
NP(Q4N6P1)
PQ(Q3N7P1)
PN(Q4N6P1)
PP(Q4N7P0)

You can build a tree!