Question

Find the sum of first 20 terms of an ap series 22+7+12 using formula

Answer 1

$\textbf{Answer:-}$

• 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.