Question

for any positive integer n the sum of the first n positive integers equals n(n+1)/2. what is the sum of all the even integers between 99 - 301? a) 10 100 b) 20 200

Answer 1

sum=(n/2)(a+l). even nos between 99. 301 =101 50.5(100+300)=20200
here n=44. sum =22(12+98)=2420 exclusive 10. 100
n=89 sum =44.5(22+198)=9790 exl 20. 200