Question

How many terms are there in the A.P. 41, 38, 35, ......, –1?

Answer 1

Here $$a = 41$$ and $$d = 38 - 41 = -3$$. 

Let there be n terms.

Last term: $$41 + (n - 1) \times (-3) = -1$$. 

So $$44 - 3n = -1$$, giving $$n = 15$$. 

Hence the A.P. has 15 terms.