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Question:

The sum 1 + 1³ + 2³ / (1 + 2) + 1³ + 2³ + 3³ / (1 + 2 + 3) + ... + 1³ + 2³ + 3³ + ... + 15³ / (1 + 2 + 3 + ... + 15)

1860

660

620

1240

Solution:

Correct option is D.620Sum=∑n=11513+23+.1531+2+.+n−1;2.15.162=∑n=115n(n+1)2−6;0=∑n=115