Difficulty: Easy
Correct Answer: 385
Explanation:
Given data
Concept / Approach
Step-by-step calculation
S = 10 × 11 × 21 / 6= (10 × 11 = 110); 110 × 21 = 23102310 ÷ 6 = 385
Verification
Manual partial sums (1^2+…+5^2 = 55; 6^2+…+10^2 = 330) ⇒ total 385.
Final Answer
Sum = 385.
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