Round Numbers
(In). In whole numbers, without regarding the fractions.
Thus we say the population of the British Isles is forty millions in
round numbers, and that of London four millions (1895). The idea is
that what is round is whole or perfect, and, of course, fractions,
being broken numbers, cannot belong thereto.
Source: Dictionary of Phrase and Fable, E. Cobham Brewer, 1894 More on Round Numbers from Fact Monster:
 Rounding Numbers  Rules & Examples For Fractions & Sums  Rounding numbers rules including fractions and sums examples.
 Numbers: Mean, median, prime numbers, rounding  Learn about mean and median, rounding, Pi, Roman Numerals, rational and irrational numbers, prefixes, and more.
 Colonial Population Estimates  Colonial Population Estimates (in round numbers) Year Population 1610 350 1620 2,300 1630 4,600 ...
 Homework Center: Numbers and Formulas  Subjects » Geography » History » Language Arts » Mathematics » ...
