Question

Which term in the A.P. $5,2,-\mathrm{1.......}$ is $-22$? Find the sum of these terms.

• A. $-85$
• B. $-75$
• C. $-95$
• D. None

Answer 1

Answer: (A)

$-85$

$a_n=-22$; $a_1=5$

$d=a_2-a_1=2-5=-3$

$\Rightarrow a_n=a+(n-1)d$

$\Rightarrow -22=5+(n-1)(-3)\Rightarrow 3n=22+5+3=30$

$\Rightarrow n=10$.

$S_{10}=\frac{10}{2}[5-22]=-85$