Answer:
1 999 000
Step-by-step explanation:
Formula:
[tex]1+2+3+.\ .\ .+n=\frac{n\times \left( n+1\right) }{2}[/tex]
………………………………………
Then
[tex]1+2+3+....+1997+1998+1999=\frac{1999\times \left( 1999+1\right) }{2}[/tex]
[tex]1+2+3+....+1997+1998+1999=\frac{1999\times \left( 2000\right) }{2}[/tex]
[tex]1+2+3+....+1997+1998+1999=\frac{3998000 }{2}[/tex]
[tex]1+2+3+....+1997+1998+1999=1999000[/tex]
