According to Baidu education data, one meter is equal to 1000 mm, and through calculation: 900÷ 1000=0.9 m, so 900mm is equal to 0.9 m, without one meter.

Millimeter, also known as millimeter, is the unit of length and rainfall, abbreviated as mm in English. 1 0mm is equivalent to 1 cm, 1 00mm is equivalent to1decimeter, and1000mm is equivalent to1meter. "meter" is the basic unit of length in the international system of units, with the symbol m, and one meter is equal to 10 decimeter. It can be used to measure length, width and height. The definition of "meter" originated in France.