An arithmetic sequence has its 5th term equal to 22 and its 15th term equal to 62. Find the 100th term
402
: a5 = a + ( 5 – 1 )d = 22 ------------ ( i )
a15 = a + (15 – 1)d = 62 ------------------- (ii)
(ii) – (i) ⇒ 62 – 22 = 14d – 4d = 10d
d = 4
Now, a + ( 5 – 1 )4 = 22
a = 6
Now, a100 = 6 + (100 – 1)4 = 402