EXAMPLE 2 Roundoff errors

Did you check Table 10.1 for consistency? The total number of people should be

24,458 + 62,240 + 34,919 + 20,790 + 42,256 + 24,623 = 209,286 (thousands)

But the table gives the total as 209,287. What happened? Each entry is rounded to the nearest thousand. The rounded entries don’t quite add to the total, which is rounded separately. Such roundoff errors will be with us from now on as we do more arithmetic.