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Q : 1     Find the sum of the following APs:

             (i)  \small 2,7,12,..., to \small 10 terms.

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Given AP is 
 \small 2,7,12,..., to \small 10 terms
Here, a = 2 \ and \ n = 10
And
d = a_2-a_1=7-2=5
Now, we know that 
S = \frac{n}{2}\left \{ 2a+(n-1)d \right \}
\Rightarrow S = \frac{10}{2}\left \{ 2\times 2 +(10-1)5\right \}
\Rightarrow S = 5\left \{ 4 +45\right \}
\Rightarrow S = 5\left \{ 49\right \}
\Rightarrow S =245
Therefore, the sum of AP  \small 2,7,12,..., to \small 10 terms is 245

Posted by

Gautam harsolia

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