Answer:
1000000
Explanation:
Finding the sum of first 'n' odd numbers:
1 to 2000.
Here, We don't know how many odd numbers are there. We can find the number of odd numbers using the below formula,

1,3,5,.........1999
aₙ = 1999 ; a = first term = 1
Common difference = d = 2
1 + (n -1)* 2 = 1999
Subtract 1 from both sides,
(n -1) *2 = 1999 -1
(n -1)*2 = 1998
Divide both sides by 2,
n - 1 = 1998 ÷ 2
n - 1 = 999
Add 1 to both sides,
n = 999 + 1
n = 1000

= 1000 * 1000
= 1000000