NDA 2026 · PYQ · Binomial Coefficients · medium
What is the greatest value of r satisfying the inequality ¹⁵C_{r+1} > 2 × ¹⁵C_r?
- A.2
- B.3
- C.4✓ Correct
- D.5
¹⁵C_{r+1}/¹⁵C_r = (15 − r)/(r + 1) > 2 gives 15 − r > 2(r + 1), i.e., 15 − r > 2r + 2, so 13 > 3r, giving r < 13/3 ≈ 4.33. The greatest integer value is r = 4.
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