9×9-1 = 80
98×9-2 = 880
987×9-3 = 8880
则: 9876 × 9 - 4={#blank#}1{#/blank#}
{#blank#}2{#/blank#}× {#blank#}3{#/blank#}-{#blank#}4{#/blank#}=888880
6×4=24 6.6×3.4=22.44 6.66×33.4=222.444
6.666×333.4={#blank#}1{#/blank#}
6.6666×3333.4={#blank#}2{#/blank#}