Question

find the number of the terms in each of the following APs

$18 ,\: \: \: \: 15 \frac{1}{2} \: \: \: 13 ,\: \: \: \: \: \: \: - 47$
​

Answer 1

as Tn=a+(n-1)d

here a=18

d=31/2-18=-5/2

and Tn=-47

putting values in relation

we get (n-1)= 65×2/5

n-1=26

n=27

there are 27 terms in given ap