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 CShow Answer
Solution(By Apex Team)
$\begin{array}{l}\text{7th term (a7) = a + 6d = 34}\\
\text{13th term (a13) = a + 12d = 64}\\
\text{Subtracting, 6d = 30 ⇒ d = 5}\\
\text{and a + 12 x 5 = 64}\\
\text{⇒ a + 60 = 64}\\
\text{⇒ a = 64 – 60 = 4}\\
\text{18th term (a18)}\\
\text{= a + 17d}\\
\text{= 4 + 17 x 5}\\
\text{= 4 + 85}\\
\text{= 89}\end{array}$
Related Questions On Progressions
How many terms are there in 20, 25, 30 . . . . . . 140?
A. 22B. 25
C. 23
D. 24
Find the first term of an AP whose 8th and 12th terms are respectively 39 and 59.
A. 5B. 6
C. 4
D. 3
Find the 15th term of the sequence 20, 15, 10 . . .
A. -45B. -55
C. -50
D. 0
The sum of the first 16 terms of an AP whose first term and third term are 5 and 15 respectively is
A. 600B. 765
C. 640
D. 680