kolminumeroisia

Kolminumeroisia is a Finnish mathematical term used to describe integers that have exactly three digits in their decimal representation. In English, these are called three-digit numbers. The term is common in early-number instruction and place-value education in Finnish schools.

Positive kolminumeroisia range from 100 to 999. There are 900 such numbers. In a three-digit number, the hundreds digit cannot be zero; it takes values from 1 to 9, while the tens and units digits can be any digit from 0 to 9. A convenient way to express a three-digit number is 100a + 10b + c, where a ∈ {1,...,9} and b, c ∈ {0,...,9}. Some discussions also consider negative numbers of three digits by magnitude, i.e., -999 to -100, when counting by absolute value.

Common uses of the concept include reinforcing place value, rounding to the nearest hundred, and estimating sums or differences involving three-digit numbers. Three-digit numbers also appear in discussions of digit sums, number ranges, and probability exercises that sample from 100 through 999.

Etymology: kolmi- means three, numero comes from number, and the suffix -isia/-isia describes a class or type in Finnish grammar. The term thus categorizes numbers by their digit length in decimal notation.

See also: two-digit numbers, four-digit numbers, decimal notation, place value.