Q. 21

# Mark the correct alternative in the following:

If , then the value of *r* is

A. 12

B. 8

C. 6

D. 10

E. 14

Answer :

r – 6 + 3r + 1 = 43 ( ^{n}C_{x =} ^{n}C_{y} ⇒ n = x + y or x = y )

4r – 5 = 43

4r = 48

r = 12

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