Question

Find 20th term from the last of the ap 3 8 13 dotdotdot 253

Answer 1

To find nth term in AP (arithmetic progression) formula=a+(n-1)d
Where a=first term ,n=required term,d=difference between 2 successive terms
In the given problem a=3,n=20,d=5(ie:8-3)
Therefore 20th term =3+(20-1)*5
=3+19*5=3+95=98

Answer 2

Solution :

We have, l = Last term = 253

and,

               d = Common difference = 8 - 3 = 5

∴ 20th term from the end = l - (20 - 1)d

                                           = l - 19d

                                           = 253 - 19 × 5

                                           = 253 - 95 = 158