Question

Find the value of the middle most terms of the AP :-13,-9,-5,-1.....51

Answer 1

common difference = -9+13 =4
first term =-13
tn=a+(n-1)d
51 =-13+(n-1)4

64=4(n-1)
n=17
hence its mean 9th term is middle
t9=-13+(9-1)4
= -13+32=19
hence middle term is 19

Answer 2

AP:-13,-9,-5,-1,........,51.
a=-13
d=-9-(-13)
d=4
last term (l)=51
l=a+(n-1)*d
51=-13+(n-1)*4
64=(n-1)*4
n-1=16
n=17
Hence, the AP has 17 terms.
Middlemost term=9th
a9=a+(n-1)*d
a9=-13+(9-1)*4
a9=-13+32
a9=19