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Question
Find the sum of the following Aps:
i) 2, 7, 12, 17, ……. to 19 terms .
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Solution
The given AP is 2, 7, 12, 17,………
Here, a= 2 and d = 7 - 2 = 5
Using the formula . `s_n = n/2 [ 2a + (n-1) d] ,`we have
`s_19 = 19/2 [ 2xx2 +(19-1) xx5]`
`= 19/2 xx (4+ 90)`
`= 19/2 xx 94`
= 893
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