4.设这水桶重x千克
x-1/10x=9
(1-1/10)x=9
x=9÷9/10
x=10
方法29÷(1-1/10)=10(kg)
5.15/16÷3=15/16×1/5=3/1612/25÷8=12/25×1/8=3/50
8÷4/5=8×4/5=1021/40÷7/8=21/40×8/7=3/5
16÷2/17=16×17/2=1367/24÷6/49=7/24×17/2=343/144
18/35÷0.6×2/34/9×15/16÷5/6
=35/18×10/6×2/3=5/12×6/5
=6/7×2/3=1/2
=12/21=4/7
(2-0.6)÷7/1535/64÷(1/8+3/4)
=1.4×15/7=35/64÷7/8
=3=35/64×8/7
=5/8
6.(1500+1000)×3/5=1500(元)
7.48+48÷4/5=108(万台)
8.方法1.设南北相距x千米
52/55x=5200
x=5500
方法2.5200÷52/55=5500(km)