Let E   &   F be two independent events. The probability that E   &   F happen…

Let E & F be two independent events. The probability that E & F happen is 112 and the probability that neither E nor F happens is 12 , then a value of PEPF is:
  1. 43
  2. 13
  3. 32
  4. 512

Solution

PEF=PE. PF=112

xy=112

PE-F-=PE- . PF-=12

 1-PE 1-PF=12

1-x-y+xy=12

1-x-y+112=12

1-x-y=12-112=512

x+y=712

x+112x=712

12x2+112x=712

12x2-7x+1=0

12x2-4x-3x+1=0

4x3x-1-13x-1=0

x=13, x=14

y=14, y=13

xy=1314 & 1413

xy=43 & 34

Asked in: JEE Main 2017 (09 Apr Online)

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