计算下面各题，能简便的要用简便方法计算21÷(13+25)÷911920÷[12×(45+25)]5.65-6.29+5.35-2.713.7×99+3.7．

Question

计算下面各题，能简便的要用简便方法计算
21÷((1)/(3)+(2)/(5))÷(9)/(11)
(9)/(20)÷[(1)/(2)×((4)/(5)+(2)/(5))]
5.65-6.29+5.35-2.71
3.7×99+3.7．

Answer 1

（1）21÷((1)/(3)+(2)/(5))÷(9)/(11)
=21÷(11)/(15)÷(9)/(11)
=21÷（(11)/(15)×(9)/(11)）
=21÷(3)/(5)
=35；

（2）(9)/(20)÷[(1)/(2)×((4)/(5)+(2)/(5))]
=(9)/(20)÷[(1)/(2)×(6)/(5)]
=(9)/(20)÷(3)/(5)
=(3)/(4)；

（3）5.65-6.29+5.35-2.71
=（5.65+5.35）-（6.29+2.71）
=11-9
=2；

（4）3.7×99+3.7
=3.7×（99+1）
=3.7×100
=370．