### If 7th and 13th terms of an A.P. be 34 and 64 respectively, then its 18th term is

A. 87 B. 88 C. 89 D. 90 Answer: Option C

### Solution(By Apex Team)

$\begin{array}{l}\text{7th term (a7) = a + 6d = 34}\\ \text{13th term (a13) = a + 12d = 64}\\ \text{Subtracting, 6d = 30 ⇒ d = 5}\\ \text{and a + 12 x 5 = 64}\\ \text{⇒ a + 60 = 64}\\ \text{⇒ a = 64 – 60 = 4}\\ \text{18th term (a18)}\\ \text{= a + 17d}\\ \text{= 4 + 17 x 5}\\ \text{= 4 + 85}\\ \text{= 89}\end{array}$

A. 22
B. 25
C. 23
D. 24

A. 5
B. 6
C. 4
D. 3

A. -45
B. -55
C. -50
D. 0