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Question
Find the sum of the following arithmetic progression :
1, 3, 5, 7, ... to 12 terms
Solution
1, 3, 5, 7 ... to 12 terms
\[\text { We have }: \]
\[ a = 1, d = \left( 3 - 1 \right) = 2\]
\[n = 12\]
\[ S_n = \frac{n}{2}\left[ 2a + (n - 1)d \right]\]
\[ = \frac{12}{2}\left[ 2 \times 1 + (12 - 1)(2) \right]\]
\[ = 6\left[ 24 \right] = 144\]
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