Last Activity: 11 Years ago
sum of odd terms from 1to 199
number of terms is =100 (tn=a +(n-1)d)a=1;d=2;tn=199
Sn(odd)=n/2[a+l]=50*200=10000
now deduct the term which are multiples of 5
a=5
d=10
tn=>195=5+(n-1)10
n=10
Sn=n/2[a+l]
5*200=1000
.:.total=10000-1000=9000
1+2+............+200=n/2(a+l)=200/2(1+200)=100(201)=20100-10100(div by 2)=10000, 10000-(5+15+......195)=10000-20/2(5+195)=10000-2000=8000
Prepraring for the competition made easy just by live online class.
Full Live Access
Study Material
Live Doubts Solving
Daily Class Assignments
Get your questions answered by the expert for free
Last Activity: 2 Year ago(s)