On a game show, there are 10 keys in a bag, and 3 of the keys start a car. A contestant randomly chooses a key. It does not start the car. She returns the key to the bag, the host mixes up the keys, and she randomly selects another key. This key does not start the car either. What is the probability of this no start, no start outcome?
(Points : 1)
Option A: 49/100

Option B: 7/15

Option C: 21/50

Option D: 9/100

Question

On a game show, there are 10 keys in a bag, and 3 of the keys start a car. A contestant randomly chooses a key. It does not start the car. She returns the key to the bag, the host mixes up the keys, and she randomly selects another key. This key does not start the car either. What is the probability of this no start, no start outcome?
(Points : 1)
       Option A: 49/100

       Option B: 7/15

       Option C: 21/50

       Option D: 9/100

welshfella · Answer

this is a sequence of independent events so you multiply the individual probabilities

welshfella · Answer

what is the probability  of choosing a key that will not open a car  with one pick?

anonymous · Answer

5

welshfella · Answer

3/10 is probability for picking a key which opens a car

anonymous · Answer

take away the 3 that work plus the 2 that they tried gives you 5 so do I multiply 3/10 by 5/10?

anonymous · Answer

It gave me 3/20 so clearly not what I have to do xD

welshfella · Answer

no there is only 2 events  - 2 picks out of the bag
probability of picking wrong key = 1 - 3/10 = 7/10

this is the same for the first pick and the second

welshfella · Answer

these are multiplied

welshfella · Answer

no start, no start  =  7/10  *  7 /10  = ?

anonymous · Answer

49/100 But im still a little confused

welshfella · Answer

49/100 is correct

can you understand why  the prob for no start = 7/10?

there are 7 keys which wont start the car out of a total of 10

anonymous · Answer

Oooh yea okay I got it. Sorry /.\

Thank you!!!

welshfella · Answer

yw