CA Foundation · Quantitative Aptitude · Sequence and Series
The value of the sum of Σ (from r = 1 to 10) of (2r + 3) is:
The sum is 140. Splitting the sigma gives 2 times the sum of the first ten natural numbers, which is 110, plus 3 added ten times, which is 30. Together this equals 140, matching the AP sum check.
- A130Correct
- B140
- C110
- D160
Explanation
Σ2r = 2×(10×11/2) = 110. Σ3 over 10 terms = 30. Total = 110 + 30 = 140. Check: AP with first term 5, last term 23, 10 terms gives 10×(5+23)/2 = 140. Option 110 omits the constant part.
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