Opening number is a standard of printing industry in China. It takes a complete printing paper as the benchmark for folding-there are several benchmarks, so we sometimes see such statements as 16 open and 32 open.

A4 and B5 are ISO international standards, and there are three series of ABC. A series is folded based on A0, which is strictly defined as1189mm * 841mm (1m2).

There are only close but no overlapping specifications between the two sets of standards, which can be said to be different.

A4 picture book 1 is rich in questions, novel in content and interesting in knowledge penetration. At the same time, through ladder training, children can fully enjoy the fun of learning in the process of receiving knowledge, so as to comprehensively improve their intelligence, enrich the mathematics knowledge of kindergarten children in large classes, and lay a good foundation for future mathematics learning.