Question

20.9×2.5一0.9X25用简便计算怎么写？

Answer 1

转化出公因数，然后利用乘法分配律来进行简便计算。
20.9×2.5-0.9×25
=2.09×10×2.5-0.9×25
=2.09×25-0.9×25
=(2.09-0.9)X25
=2X25
=50

Answer 2

20.9×2.5一0.9×25
＝20.9×2.5一9×2.5
＝2.5×(20.9一9)＝2.5×11.9
＝29.75

Answer 3

20.9×25-0.9×25
=25×（20.9-0.9）
=25×20
=500

Answer 4

20.9×2.5-0.9×25
=2.09×25-0.9×25
=（2.09-0.9）×25
=1.19×25
=（1.2-0.01）×25
=1.2×25-0.01×25
=30-0.25
=29.75
整个计算就是用了结合律

Answer 5

20.9×2.5－0.9×25
=20.9×25×0.1－0.9×25
=25×（20.9×0.1－0.9）
=25×（2.09－0.9）
=25×1.19
=29.75