We are given 42,099
To round off to the nearest thousand, we need to check the hundredth digit
Ten thousandth digit = 4
Thousandth digit = 2
Hundredth = 0
Tenth = 9
Unit = 9
If the hundredth digit is 0, 1, 2, 3 and 4, then you need to round off to the previous thousand
The answe is 42, 000