Question

脱式计算，能简算的要简算． 2.31×1.5+1.5×7.69	23.4÷7.8-2.1	4.5×0.4÷4.5×0.4
6.4×101-6.4	4×1.98×0.25	7.5+2.5-7.5+2.5．

Answer 1

（1）2.31×1.5+1.5×7.69
=（2.31+7.69）×1.5
=10×1.5
=15；

（2）23.4÷7.8-2.1
=3-2.1
=0.9；

（3）4.5×0.4÷4.5×0.4
=4.5÷4.5×0.4×0.4
=1×0.4×0.4
=0.16；

（4）6.4×101-6.4
=6.4×（101-1）
=6.4×100
=640；

（5）4×1.98×0.25
=4×0.25×1.98
=1×1.98
=1.98；

（6）7.5+2.5-7.5+2.5
=7.5-7.5+（2.5+2.5）
=0+5
=5．