    Question

# To find the sum of the first 24 terms of an AP whose nth term is given by an=3+2n, what is the best approach to solve this question?

A
Find the first term and the common difference.
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B
List out the first 24 terms using the expression for nth term and add them.
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C
Data insufficient - we need the value of “first term” to be given.
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D
Data insufficient - we need the value of “common difference” to be given.
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Solution

## The correct option is A Find the first term and the common difference.We know that we have two formulae for finding Sum to n terms of an AP. Sn=n2(2a+(n−1)d) where Sn is the sum of n terms of the AP, 'n' is the number of terms of the AP, 'a' is the first term of the AP 'd' is the common difference. Also, Sn=n(first term+last term)2 Given an=3+2n Therefore, a1=5, a2=7, a3=9.......a24=51 First term = 5, 24th term = 51, d= 2 Hence, s24=242(2(5)+23(2)) = 12(56) = 672  Suggest Corrections  0      Similar questions  Related Videos   Sum of First N Natural Numbers
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