2.5X9.1X4 16.2X99+16.2 5.1X0.9+0.9X4.9 1.7X15.7+15.7X8.3能简便就简便

Question

如题所述

Answer 1

2.5
*
9.1 *
4
=
(2.5
*
4)
*
9.1
=
10
*
9.1
=
91
用到了乘法交换律和乘法结合律
16.2
*
99
+
16.2
=
16.2
*
(99
+
1)
=16.2
*
100
=
1620
用到了乘法分配律
5.1
*
0.9
+
0.9
*
4.9
=
5.1
*
0.9
+
4.9
*
0.9
=
(5.1
+
4.9)
*
0.9
=
10
*
0.9
=
9
1.7
*
15.7
+
15.7
*
8.3
=
1.7
*
15.7
+
8.3
*
15.7
=
(1.7
+
8.3)
*
15.7
=
157
后面两题用到了乘法交换律和乘法分配律