Question

Find the sum of odd integer between 1 and 2001.

Answer 1

Step-by-step explanation:

Here a = 3 , d = 2 , l = 1999

l = a + ( n - 1 )d

1999 = 3 + (n - 1)2

1999 = 3 + 2n - 2

1999 = 1 + 2n

1999 - 1 = 2n

1998/2 = n

n = 999

Sn = n/2 ( 2a + ( n - 1)d

= 999/2 ( 2*3 + (999 - 1) 2

= 999/2 ( 6 + (998) 2)

= 999/2 ( 6 + 1996)

= 999/2 ( 2002 )

= 999 * 1001

Sn = 999,999