2000 is 901 from 1099 whereas 1000 is only 99. Clearly 1000 is closer.
1099
To the nearest hundred, 1100 To the nearest thousand, 1000
Observe that: 100+999 =1099, 101 + 998 = 1099 up to 549+550=1099. So 1099 * (1000-100/2) or 1099 * 450 (450 pairs of numbers that sum to 1099) or 494,500. This is a variant of the method exposed in the "Gauss Anecdote"
The next integer is 1100.
The year 1031 was the 11th century (years 1000-1099).
The year 1066 was the 11th century (years 1000-1099).
1000
The first crusade took place in the year 1000.
2000 (1000+1000=2000)
2000
= 2000
1678 to the nearest 1000 would be 2000. This is because 1678 is closer to 2000 than it is to 1000. When rounding to the nearest 1000, you look at the hundreds place - in this case, the hundreds place is 6, which is closer to 10 (in 2000) than to 0 (in 1000).