If the 2nd terms of an AP is 13 and 5th term is 25, what is its 7th term?
As we know, nth term of an AP is
an = a + (n - 1)d
where a = first term
an is nth term
d is the common difference
a2 = a + d = 13 …..(1)
a5 = a + 4d = 25 ……(2)
Solving 1 and 2
From 1 we have
a = 13 - d
using this in 2, we have
13 - d + 4d = 25
13 + 3d = 25
3d = 12
d = 4
a = 13 - 4 = 9
a7 = a + 6d
= 9 + 6(4)
= 9 + 24 = 33