A bag contains 5 blue and an unknown number x of red balls. Two balls are drawn at random. If the…

A bag contains 5 blue and an unknown number x of red balls. Two balls are drawn at random. If the probability of both of them being blue is 514, then the value of x is equal to
  1. 8
  2. 5
  3. 3
  4. 6

Solution

P=5C25+xC2=514

⇒10×2(5+x)(4+x)=514

⇒x2+20+9x=14×4

⇒x2+9x-36=0

⇒x=3, -12

Asked in: AP EAMCET 2020 (23 Sep Shift 1)

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