6.24*9+6.24可以简化成6.24*(9+1)=6.24*10=62.4
6.24×9.9+6.24=6.24×(9.9+1)=6.24×10.9=6.24×(10+1-0.1)=68.016
6.24×9.9+6.24=6.24×(9.9+1)=6.24×10.9=6.24×(10+1-0.1)=62.4+6.24-0.624=68.016
按部就班进行计算是最简便的计算;6.24×9.9+6.24=61.776+6.24=68.016