用递等式算一算.
| 12.9-4.12-5.88 | 0.4×13+ ×7 | ÷ ×![]() | ÷[ ×( - )] |
(1)12.9-4.12-5.88,
=12.9-(4.12+5.88),
=12.9-10,
=2.9;
(2)0.4×13+
×7,=0.4×13+0.4×7,
=0.4×(13+7),
=0.4×20,
=8;
(3)
÷
×
,=
×
,=
;(4)
÷[
×(
-
)],=
÷[
×
],=
÷
,=2.
分析:(1)根据连减的性质进行简算;
(2)根据乘法分配律进行简算;
(3)先算除法,再算乘法;
(4)先算减法,再算乘法,最后算除法.
点评:考查了运算定律与简便运算,四则混合运算.注意运算顺序和运算法则,灵活运用所学的运算律简便计算.