Mark the correct alternative in the following: If , then is equal to

Question

Philoid · Accepted Answer

r + r – 10 = 20 ( ⁿC_{x =} ⁿC_y ⇒ n = x + y or x = y )

2r – 10 = 20

2r = 30

r = 15

Now,

¹⁸C_r = ¹⁸C₁₅

¹⁸C₁₅ = ¹⁸C₃

¹⁸C₃