CA Foundation · Quantitative Aptitude · Sequence and Series
What is the sum of the series 1² + 2² + 3² + ... + 12² minus the sum 1 + 2 + 3 + ... + 12?
The sum of squares of the first 12 natural numbers is 650 and the sum of the numbers themselves is 78. Subtracting gives 572, which is the required value.
- A650
- B572Correct
- C728
- D78
Explanation
Sum of squares = 12×13×25/6 = 650. Sum of first 12 natural numbers = 12×13/2 = 78. Difference = 650 − 78 = 572. Option 650 ignores the subtraction, and 728 wrongly adds the two sums.
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