Xavier Aptitude Test 2015 Paper

Question : 52 of 113

Marks: +1, -0

What is the sum of the following series ?
- 64, - 66, - 68, ........, - 100

Solution:

(b) The given series is an A.P.

a=-64, l=-100, d=-2

l=\ {a}+( {n}-1) \ {d} \⇒-100=-64+(\ {n}-1)(-2)

⇒ 2n = 100 – 64 + 2 ⇒ n = 19

S_{n}= {n}/{2}(a+ l)= {19}/{2}(-64-100)=-1558

Go to Question:

Prev Question

Next Question