Binomial Theorem
Properties of Binomial Coefficients
Premium Question
Grade 11
Question:
If $\binom{20}{r} = \binom{20}{r + 6}$, then the value of $r$ equals _____.
Step-by-Step Solution
Key Concept: Recall that $\binom{n}{a} = \binom{n}{b}$ forces either $a = b$ or $a + b = n$ — since $r \neq r + 6$, use the second condition with $n = 20$ to form a linear equation in $r$.
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Correct Answer: 7