Question

42✘2.8+5.7✘28+2.8用简便计算方法？

Answer 1

42✘2.8+5.7✘28+2.8
=42x2.8+5.7x10x2.8+2.8
=2.8x（42+57+1）
=2.8x100
=280

Answer 2

42×2.8+5.7×28+2.8
=42×2.8+5.7×10×2.8+2.8
=（42+5.7×10+1）×2.8
=100×2.8
=280