The sum $1 + \frac{1^3 + 2^3}{1 + 2} + \frac{1^3 + 2^3 + 3^3}{1 + 2 + 3} + \dots$ up to 15 terms is:
Step-by-Step Solution
Key Concept: The $n$-th term is $\frac{[n(n+1)/2]^2}{n(n+1)/2} = \frac{n(n + 1)}{2}$. Sum $\sum_{n=1}^{15} \frac{n(n+1)}{2}$ using standard formulas.
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Correct Answer: (3)