What is the sum of a 22-term arithmetic sequence where the first term is 55 and the last term is -29?
Choose one answer.
a. 260
b. 286
c. 312
d. 338

Question

What is the sum of a 22-term arithmetic sequence where the first term is 55 and the last term is -29?
Choose one answer.
	a. 260 	
	b. 286 	
	c. 312 	
	d. 338

parthkohli · Answer

$\Large \color{Black}{\Rightarrow {n \over 2}({a_1 + a_n}) }$
This is the formula. Let's substitute right there.

$\Large \color{Black}{\Rightarrow {22 \over 2}(55 + -29) }$

$\Large \color{Black}{\Rightarrow 11(55 - 29) }$

$\Large \color{Black}{\Rightarrow 11(26) }$

$\Large \color{Black}{\Rightarrow 286 }$

anonymous · Answer

use sum formula

Sn = [n(a1 + an)]/2

anonymous · Answer

K thanks!