Integers -4, -3, -2, -1, 0, 1, 2, 3, 4… all the whole numbers and their opposites (the positive whole numbers, the negative whole numbers, and zero). Fractions and decimals are not integers. For example, -5 is an integer but not a whole number or a natural number.
so it depends which rectangle came first. if it started as large and was dilated to the smaller one, then the ratio is (.5/2.5) which simplifies to 1/5 or 0.2.