3×{#blank#}1{#/blank#}=15         {#blank#}2{#/blank#}×5=25           9×{#blank#}3{#/blank#}=3621

4×{#blank#}4{#/blank#}=2×6       4×{#blank#}5{#/blank#}=2×8        {#blank#}6{#/blank#}×8=4×6

计算54÷9时想口诀{#blank#}3{#/blank#}，商是{#blank#}4{#/blank#}．

{#blank#}1{#/blank#}×8<40              6×{#blank#}2{#/blank#}<40            27>3×{#blank#}3{#/blank#}

{#blank#}4{#/blank#}×9<81              5×{#blank#}5{#/blank#}<35            28>7×{#blank#}6{#/blank#}