CSL105 quiz2:

A bag contains either a 100 Rs note or a 500 Rs note, with equal probability.
I add a 100 Rs note to the bag. (I'm rich).

'A' draws a note from the bag and it is Rs 100. 'A' keeps it.

'B' draws a note now. What is the probability that 'B' draws a 100 Rs note?

Answer=2/3.

15 comments:

  1. CSL105 is a tough course when it comes to the difficulty of problems asked.
    Think again.

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  2. Does answer contain log term
    Mind it, neither I have said nor I have got the answer. Just a friend told me to confirm it(he was not joking)

    But I personally feel answer is 1/2.

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  3. arre yr, simple enough, its 2/3 only

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  4. we have to find P(A intersection B)/P(A)

    both A and B will draw a 100 Rs note only in if there was a 100 Rs note already present->P(A intersection B)=1/2

    P(A)=(1/2)(1/2)......[if there was 500 rs note initially] + (1/2)(1).....[if there was 100 rs note initially]=3/4

    divide to get 2/3

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  5. cant we do this by simply making cases????if we can.....pls post that approach

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  6. Pratik yaar probability module jab ho jayega tumhara tab u will find it easy, no need to trouble urself rite now

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  7. Bhaiya please post some more questions of maths also, would be fun for a change

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