Question
Find the sum of first 24 terms of the A.P. whose nth term is given by an=3+2n
Answer: Option D
:
D
As an=3+2n,
so,
a1=3+2×1=5
a2=3+2×2=7
a3=3+2×3=9
List of numbers becomes 5, 7, 9, 11 . . .
Here, 7–5=9–7=11–9=2 and so on.
So, it forms an AP with common difference d=2.
To findS24, we have n=24,a=5,d=2.
Therefore, S24=242(2(5)+(24−1)2)
=12(10+46)=672
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:
D
As an=3+2n,
so,
a1=3+2×1=5
a2=3+2×2=7
a3=3+2×3=9
List of numbers becomes 5, 7, 9, 11 . . .
Here, 7–5=9–7=11–9=2 and so on.
So, it forms an AP with common difference d=2.
To findS24, we have n=24,a=5,d=2.
Therefore, S24=242(2(5)+(24−1)2)
=12(10+46)=672
Was this answer helpful ?
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