Question

In the given arithmetic progression, find the value of r.
3, p, q, 9, r

• A. 13
• B. 14
• C. 11
• D. 15

Answer 1

The correct option is C 11

$n^{th}$ term, $a_n=a+(n-1)d$
$a_4=3+(4-1)d$ [∵ $a=3$, $a_4=9$]
9 = 3 + 3d
9 - 3 = 3d
d = 2

r is $5^{th}$ term of the AP.
$\therefore a_5=3+(5-1)2=3+8=11$
$a_5=3+8=11$
$a_5=11$
$\therefore$ Value of r is 11.