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JEE Main20208 Jan 2020Morning ShiftMathematicsBinomial TheoremActual

If a , b and c are the greatest values of C p 19 , C q 20 and C r 21 respectively, then:

Options

  1. Aa 11 = b 22 = c 21
  2. Ba 10 = b 11 = c 21
  3. Ca 11 = b 22 = c 42
  4. Da 10 = b 11 = c 42

Correct answer

C. a 11 = b 22 = c 42

Step-by-step solution

We know that,   n C r is maximum at middle term. a =     19 C p =   19 C 10 =   19 C 9 b =     20 C q =   20 C 10 c =     21 C 6 =   21 C 10 =   21 C 11 Hence, a   19 C 9 = a 20 10 .   19 C 9 = a 21 11 . 20 10 .   19 C 9 ⇒ a 1 = b 2 = c 42 11 ⇒ a 11 = b 22 = c 42

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