Question

Find the fourth term from the end of the AP 7,10,13.......,184

Answer 1

7,10,13,(16)........184

Answer 2

You have
a = 7,
d = 3,
last term = 184

I am telling you a trick which i used when in 10th class for this sort of questions.

Just flip the A.P.
so, you got, new AP as 184,.........13,10,7
that means now you have →
a = 184
d = -3
and last term = 7

Now , you have to calculate 4th term from starting.

So, put the formula
a4 = a + (4-1)d
therefore, a4 = 184 + 3(-3)
. a4 = 175

This was 4th term from last of the original AP

Trust me this trick is easier to remember than the formula. you can solve almost every question and no teacher can cut your marks.

Hope this helps:)