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Each of the cards in a deck of 50 cards has a number from 1 to 20

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Each of the cards in a deck of 50 cards has a number from 1 to 20 [#permalink]

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New post 25 Jun 2016, 04:23
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Question Stats:

44% (01:55) correct 56% (01:23) wrong based on 88 sessions

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Each of the cards in a deck of 50 cards has a number from 1 to 20 written on it in either black, red or blue ink. If one card is to be selected at random from the deck, what is the probability that the card selected will either have an odd number or be written in red ink?

(1) The probability that the card will both have an off number and be written in red ink is 0.

(2) The probability that the card will have an odd number minus the probability that the card will be written in red ink is 0.4



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[Reveal] Spoiler: OA

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Re: Each of the cards in a deck of 50 cards has a number from 1 to 20 [#permalink]

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New post 26 Jun 2016, 04:56
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For those of you who were not able to answer this, here is the answer.
We know there are cards written with numbers in different probability colours. We are asked for the probability of randomly selecting a card that has either an odd or is written in red. Let us assume this prob to be x.

So, x= (prob of selecting a card with an odd number) + (prob of selecting a card written in red) - (prob of selecting a card with an odd number written in red)
or we can write the above as: x = P(odd) + P(red) - P(odd and red).

Statement 1: P(odd and red) = 0

Insufficient as we don't know P(odd) + P(red).

Statement 2: P(odd) - P(red) = 0.4

This can be true for various combination of P(odd) and P(red), for ex. P(odd)=0.5 and P(red)=0.1 or P(odd)=0.6 and P(red)=0.2 etc.

Hence, statement 2 is also insufficient!

Combining 1 and 2 also we do not have exact value of P(odd) and P(red). We just have values for P(odd)-P(red) and P(odd and red).

Therefore, the answer will be E.

--------------------------------------

P.S. Don't forget to give kudos :)
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Re: Each of the cards in a deck of 50 cards has a number from 1 to 20 [#permalink]

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New post 26 Jun 2016, 07:07
14101992 wrote:
For those of you who were not able to answer this, here is the answer.
We know there are cards written with numbers in different probability colours. We are asked for the probability of randomly selecting a card that has either an odd or is written in red. Let us assume this prob to be x.

So, x= (prob of selecting a card with an odd number) + (prob of selecting a card written in red) - (prob of selecting a card with an odd number written in red)
or we can write the above as: x = P(odd) + P(red) - P(odd and red).

Statement 1: P(odd and red) = 0

Insufficient as we don't know P(odd) + P(red).

Statement 2: P(odd) - P(red) = 0.4

This can be true for various combination of P(odd) and P(red), for ex. P(odd)=0.5 and P(red)=0.1 or P(odd)=0.6 and P(red)=0.2 etc.

Hence, statement 2 is also insufficient!

Combining 1 and 2 also we do not have exact value of P(odd) and P(red). We just have values for P(odd)-P(red) and P(odd and red).

Therefore, the answer will be E.

--------------------------------------

P.S. Don't forget to give kudos :)



Quite not understood the logic
x = P(odd) + P(red) - P(odd and red).
1) says P(odd and red)=0
so x = P(odd) + P(red) - 0= x = P(odd) + P(red)

2) says
P(odd)- P(Red)=0.4
P(odd)= 0.5 so P(red)=0.1

combine 1 and 2

x= 0.5+0.1=0.6

are we not getting a value here?
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Re: Each of the cards in a deck of 50 cards has a number from 1 to 20 [#permalink]

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New post 26 Jun 2016, 09:03
RatneshS wrote:
14101992 wrote:
For those of you who were not able to answer this, here is the answer.
We know there are cards written with numbers in different probability colours. We are asked for the probability of randomly selecting a card that has either an odd or is written in red. Let us assume this prob to be x.

So, x= (prob of selecting a card with an odd number) + (prob of selecting a card written in red) - (prob of selecting a card with an odd number written in red)
or we can write the above as: x = P(odd) + P(red) - P(odd and red).

Statement 1: P(odd and red) = 0

Insufficient as we don't know P(odd) + P(red).

Statement 2: P(odd) - P(red) = 0.4

This can be true for various combination of P(odd) and P(red), for ex. P(odd)=0.5 and P(red)=0.1 or P(odd)=0.6 and P(red)=0.2 etc.

Hence, statement 2 is also insufficient!

Combining 1 and 2 also we do not have exact value of P(odd) and P(red). We just have values for P(odd)-P(red) and P(odd and red).

Therefore, the answer will be E.

--------------------------------------

P.S. Don't forget to give kudos :)



Quite not understood the logic
x = P(odd) + P(red) - P(odd and red).
1) says P(odd and red)=0
so x = P(odd) + P(red) - 0= x = P(odd) + P(red)

2) says
P(odd)- P(Red)=0.4
P(odd)= 0.5 so P(red)=0.1

combine 1 and 2

x= 0.5+0.1=0.6

are we not getting a value here?


Hi! RatneshS,

Statement 2 can have many combinations:-
P(odd)- P(Red)=0.4
P(odd)= 0.5 so P(red)=0.1
or P(odd)= 0.2 so P(red)=0.2 and so on.

We are not getting a unique value by combining both statement.
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Re: Each of the cards in a deck of 50 cards has a number from 1 to 20 [#permalink]

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New post 22 May 2017, 10:14
Divyadisha wrote:
RatneshS wrote:
14101992 wrote:
For those of you who were not able to answer this, here is the answer.
We know there are cards written with numbers in different probability colours. We are asked for the probability of randomly selecting a card that has either an odd or is written in red. Let us assume this prob to be x.

So, x= (prob of selecting a card with an odd number) + (prob of selecting a card written in red) - (prob of selecting a card with an odd number written in red)
or we can write the above as: x = P(odd) + P(red) - P(odd and red).

Statement 1: P(odd and red) = 0

Insufficient as we don't know P(odd) + P(red).

Statement 2: P(odd) - P(red) = 0.4

This can be true for various combination of P(odd) and P(red), for ex. P(odd)=0.5 and P(red)=0.1 or P(odd)=0.6 and P(red)=0.2 etc.

Hence, statement 2 is also insufficient!

Combining 1 and 2 also we do not have exact value of P(odd) and P(red). We just have values for P(odd)-P(red) and P(odd and red).

Therefore, the answer will be E.

--------------------------------------

P.S. Don't forget to give kudos :)



Quite not understood the logic
x = P(odd) + P(red) - P(odd and red).
1) says P(odd and red)=0
so x = P(odd) + P(red) - 0= x = P(odd) + P(red)

2) says
P(odd)- P(Red)=0.4
P(odd)= 0.5 so P(red)=0.1

combine 1 and 2

x= 0.5+0.1=0.6

are we not getting a value here?


Hi! RatneshS,

Statement 2 can have many combinations:-
P(odd)- P(Red)=0.4
P(odd)= 0.5 so P(red)=0.1
or P(odd)= 0.2 so P(red)=0.2 and so on.

We are not getting a unique value by combining both statement.


Odd numbers between 1 and 20 is 10. So P(odd) = 10/50= 0.2
Am I doing something wrong?
Re: Each of the cards in a deck of 50 cards has a number from 1 to 20   [#permalink] 22 May 2017, 10:14
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Each of the cards in a deck of 50 cards has a number from 1 to 20

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