CA Foundation · Quantitative Aptitude · Sequence and Series
A sequence is defined by t(n) = 2n² − 3n + 1. What is the sum of its 3rd and 5th terms?
Substituting n = 3 and n = 5 into t(n) = 2n² − 3n + 1 gives 10 and 36 respectively. Adding these two terms gives 46, which is the required sum of the third and fifth terms.
- A46Correct
- B44
- C40
- D52
Explanation
t(3) = 2(9) − 3(3) + 1 = 18 − 9 + 1 = 10. t(5) = 2(25) − 3(5) + 1 = 50 − 15 + 1 = 36. The sum is 10 + 36 = 46. Option 44 results from taking t(5) as 34 by an arithmetic slip, and 52 from omitting the −3n term in one of the terms.
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