find sum of all ODD numbers between 0 and 50.
1st odd no.=1
last odd no.=49
a=1, an or l=49, common diff. d= 2,
an=a+(n-1)d
=1+(n-1)2=49
=1+2n-2=49
=2n-1=49
=2n=49=1
=2n=50
n=25
sn=n/2(a+l)
=25/2(1+49)
=25/2 * 50
=25*25=625
therefore sum of all odd integers between 0 to 50 is 625 :D
m of odd nos. btwn 0-50 is 625 :)