3.9×99+3.5用脱式计算？

3.9×99+3.5
=3.9×（100-1）+3.5
=3.9×100-3.9×1+3.5
=390-3.9+3.5
=390-（3.9-3.5）
=390-0.4
=389.6

3.9×99+3.5
=3.9×99+3.9-0.4
=3.9×（99+1）-0.4
=3.9×100-0.4
=390-0.4
=389.6

3.9×99+3.5
=3.9×(100-1)+3.5
=3.9×100-3.9+3.5
=390-(3.9-3.5)
=390-0.4
=389.6
望采纳，谢谢

等于389.6
3.9x99十3.5
=3.9x100-3.9+3.5
=390-0.4
=389.6
用简便计算更简单点，100个3.9减3.9等于3.9乘以99，100乘以3.9等于390，3.5减去3.9等于负0.4，390减去0.4等于389.6。