Respuesta :

9,990 first digit is like 1, then 10, then 100, then 1000 so the fourth digit being 1 goes to 0 when rounding

When rounding to the nearest thousand, you look at the following number to know if you go up or stay. In the case of 9,991:

9,991     If the 2nd largest digit is ≥ 5, then round up.

10,000

Therefore, you would round 9.991 to 10,000.

Hope this helps! :)

Edit: I literally solved for the wrong thing earlier lol; fixed it.