Question

find the sum of first 20 term of statue arethamatic series 2+7+12using suitable formula ​

Answer 1

Now we know that.

Sn = [2a + (n-1)d]

=> Sn = [2*2 + (20-1)5] => Sn = 10[4 + 19*5] =>Sn = 10(4 + 95) =>Sn = 10 * 99. => Sn = 990. Hence the sum of 20 terms of the AP is 990. Remember.

1)Sn = [2a + (n-1)d] -For finding sum till nth term of an AP. 2)An = 2a + {n-1}d. -For finding nth term of an AP.

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Answer 2

Answer:

it's arithmetic ok

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