If the coefficient of 4th term in the expansion of \( (a+b)^{n} \) is 56 , then the value of \( n \) is:
The 4th term of \((a+b)^n\) is \(T_4 = \binom{n}{3}a^{n-3}b^3\), so its coefficient is \(\binom{n}{3}\).
\(\binom{n}{3} = 56\). Since \(\binom{8}{3} = \frac{8 \cdot 7 \cdot 6}{6} = 56\), we get \(n = 8\).
Answer: (C) 8
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