9.12÷6.4=912÷640=640÷640+272÷640=1+(272÷8)/(640÷8)=1+(34÷2)/(80÷2)=1+17/40=1又40分之17
9.12÷6.4=91.2÷64=45.6÷32=22.8÷16=11.4÷8=5.7÷4=2.85÷2=1.425