Question

Find the sum of odd integers from 1 to 2001​

Answer 1

Answer:

The series of odd integers from 1 to 2001 is,

1,3,5,7..............,2001

a=1

d=3−1=2

l=2001

an=a+(n−1)d

2001=1+(n−1)2

2000=2(n−1)

∴n=1001

Sn=2n[a+l]

=21001[1+2001]

=10,02,001

Answer 2

Answer:

1,3,5,7..............,2001

a=1

d=3−1=2

l=2001

a

n

=a+(n−1)d

2001=1+(n−1)2

2000=2(n−1)

∴n=1001

S

n

=

2

n

[a+l]

=

2

1001

[1+2001]

=10,02,001