5.6乘1.25
=7x0.8x1.25
=7x1
=7
11.1除以0.25.
=11.1x4÷(0.25x4)
=44.4÷1
=44.4
457除以25除以4
=457÷（25x4）
=457÷100
=4.57
21除以1.25
=21x0.8÷(1.25×0.8)
=16.8÷1
=16.8