简便计算:18.9x178.178＋0.49 -17.8x189.189

Question

如题所述

Answer 1

18.9x178.178+0.49 -17.8x189.189
=18.9x178×1.001-17.8x189×1.001+0.49
=18.9x178×1.001-18.9×178×1.001+0.49
=0+0.49
=0.49追答

说明：
178.178
=178+0.178
=178×1+178×0.001
=178×(1+0.001)
=178×1.001

189.189
=189+0.189
=189×1+189×0.001
=189×(1+0.001)
=189×1.001