Question

9.15 (7.8-2.9)×0.8用递等式？

Answer 1

9.15×(7.8-2.9)×0.8
=9.15×4.9×0.8
=44.835×0.8
=35.868
​

Answer 2

末尾有5的先乘以偶数，减小数位，乘法可以用分配律
9.15 (7.8-2.9)×0.8
=9.15×4.9×0.8
=9.15×0.8×4.9
=7.32×4.9
=7.32×（5-0.1）
=7.32x5-7.32×0.1
=36.6-0.732
=35.868
望采纳，谢谢