Question

find the no. of terms of the ap 18,15 1/2,13,.....-49 1/2 and find the sum of all its terms

Answer 1

nth term of an AP=a + (n-1)*d
let -49.5 be the nth term.
here, a=18
d = 15.5 - 18 = -2.5
So, -49.5 = 18 + (n-1)*(-2.5)
solving this you get, n = 28.

Now sum of n terms of AP = n(a+l)/2
where l is the last term.

So, Sum of all terms = 28*(18 + (-49.5))/2
= -441

Answer 2

Answer:

Step-by-step explanation: