7. Find the sum of first 22 terms of an AP in which d= 7 and 22nd term

1.	7. Find the sum of first 22 terms of an AP in which d= 7 and 22nd term is 149.
Answer» $\textbf{\underline{\underline{According\:to\:the\:Question}}}$ d = 7 (Common difference) $\rightarrow{a_{22}=149}$ a + (22 - 1)d = 149 a + 21 × 7 = 149 a + 147 = 149 a = 149 - 147 a = 2 ★Now SUM of 22 terms :- ★Substitute the values :- n = 32 , a = 2 and d = 7 ${\boxed{\sf\:{S_{n}=\dfrac{n}{2}[2a+(n-1)d]}}}$ ${\boxed{\sf\:{S_{22}=\dfrac{22}{2}[2(2)+(22-1)7]}}}$ = 11(4 + 21 × 7) = 11(4 + 147) = 11 × 151 = 1661 ★Therefore :- $\fbox{Sum\;of\;first\;22\;term\;is\;1661}$