Question

You are given a box of 100 silver dollars, all facing heads up. You are instructed to shake the box 2 times; after each shake, you will remove all the dollars that are heads up before shaking again. You may keep all the dollars that are still tails up following the sixth shake. How many dollars will you most likely get to keep?

Answer 1

25

Answer 2

Can you explain how you got that answer?

Answer 3

By the way the options are
A.6
B.12
C.25
D.50

Answer 4

In the beginning of the question you said 2 shakes, by the end of the question you said 6 shakes. Which is it?

Answer 5

probability of a dollar remaining a heads = 1/2
Expected no. of tails remaining therefore after 1st shake = 1/2 * 100 = 50
similaryl after second shake 25

Answer 6

I am not sure as it is the question that asks for it, not I.

Answer 7

Well, after each shake, you can expect half of the dollars to be eliminated. So after n shakes the amount of dollars left is expected to be:
(1/2)^n times the original amount of dollars. So after two shakes you'll have 1/4 of the dollars left. After six shakes you'll have 1/64 left.

Answer 8

So do I multiply that with 100 in order to get the answer?

Answer 9

Kawsam, I do not mean to be rude but you just copy and pasted another persons answer to this same question.

Answer 10

well how would you know that? because u looked online too! lol. but whatever.. ill delete the comment if u wan me to.

Answer 11

No, you do not have to do that if you do not want to.

Answer 12

@Yairenis The question is bad in that it suggests two different amounts of shakes. My guess is that it wants two shakes, which would leave 1/4 of 100 or 25.

Answer 13

wait.... are u in flvs? @vinnv226

Answer 14

What is "flvs?"

Answer 15

nvm! lol its an online virtual school in florida.

Answer 16

Exactly, what I was going to say.

Answer 17

Thank you for all your help!