Question

简便计算 能简算的要简算 一定要写出计算过程 急急急！！！

305X19-1957除以19
5.13X99+0.513X10
（5/12-1/4）除以2/3X4/7
11/8除以[9/10-（2/5+1/4）]
3.78X[1除以（2.1-2.09）]
能回答一两个也可以

Answer 1

305X19-1957 ÷19
=305×19-103
=305×（20-1）-103
=305×20-305-103
=6100-（305+103）
=6100-408
=5692
5.13X99+0.513X10
=5.13×（99+1）
=5.13×100
=513
（5/12-1/4）÷2/3X4/7
=（5/12-3/12）÷2/3X4/7
=2/12÷2/3X4/7
=1/6×3/2X4/7
=1/7
11/8÷[9/10-（2/5+1/4）]
=11/8÷[9/10-（8/20+5/20）]
=11/8÷[9/10-13/20]
=11/8÷[18/20-13/20]
=11/8÷5/20
=11/8×20/5
=11/2

3.78X[1÷（2.1-2.09）]
=3.78×[1÷0.91]
=3.78×100/91
=378/91

Answer 2

5.13X99+0.513X10
=5.13×100－5。13＋5.13
=5。13×100
=513