Demonstration model for deriving calculation formulas for pi and circular area in accordance with the new curriculum standards_Demonstration model for deriving calculation formulas for pi and circular area in accordance with the new curriculum standards价格_Demonstration model for deriving calculation formulas for pi and circular area in accordance with the new curriculum standards批发_Demonstration model for deriving calculation formulas for pi and circular area in accordance with the new curriculum standards供应商-Ningbo Kaidi Science and Education Instrument Co.,