7×9和9×7是用同一句口诀计算．

算式：{#blank#}2{#/blank#}×{#blank#}3{#/blank#}＝{#blank#}4{#/blank#}

2×5 =      4 × 6 =       5 ×3 =       8 ×5 = 

5 +5 =       5×5 =        3 × 5=       2 ×9 =

7×4 =      3×6 =         6×5 =        4 ×1=

4× 8 =     7 ×3 =       4 × 4 =       4 + 4 =

4×{#blank#}1{#/blank#}＜33      7×{#blank#}2{#/blank#}＜55     28＞{#blank#}3{#/blank#}×3    55＞{#blank#}4{#/blank#}×9

{#blank#}1{#/blank#}              {#blank#}2{#/blank#}        {#blank#}3{#/blank#}