5/11×6/1000=5/11×3/500=3/110
3/110×2 1/5=3/110×11/5=3/50
1 1/8×0,004=9/8×4/1000=9/2000
9/2000×8/9=8/2000=2/500=1/250
3/50+1/250 =16/250=8/125
0,5×0,0009=0,0045
0,0001×0,5=0,00005
0,0045+0,00005=0,00455
8/125÷455/100000=
8/125×100000/455=
9100/
455=20