Bright primary school 420 1 person, about (4200). This topic belongs to the practice of approximate number in Unit 7, Volume 2, Grade 2 of Mathematics, People's Education Press.

Approximatenumber refers to a number close to an exact number. Among them, the exact number is the most original data of this number, and it is expressed without any simplification, simplification and rounding. Approximation is a number that is not much different from the original data by rounding or rounding.