题目内容
能简便要简便计算
(20.2×0.4+7.88)÷4.2 | (3.75+2.35)×9.9 | 12+7.5×36÷7.2 |
3.45×0.45+34.5×0.55 | 360÷15-2.5×1.6 | 12.5×25×0.4×0.8 |
考点:小数四则混合运算,运算定律与简便运算
专题:运算顺序及法则
分析:(1)先算括号内的乘法,再算括号内的加法,最后算括号外的除法.
(2)先算括号内的,再算括号外的.
(3)先算36÷7.2=5,再算7.5×5,最后算加法.
(4)通过数字转化,运用乘法分配律简算.
(5)先算除法和乘法,再算减法.
(6)运用乘法交换律与结合律简算.
(2)先算括号内的,再算括号外的.
(3)先算36÷7.2=5,再算7.5×5,最后算加法.
(4)通过数字转化,运用乘法分配律简算.
(5)先算除法和乘法,再算减法.
(6)运用乘法交换律与结合律简算.
解答:
解:(1)(20.2×0.4+7.88)÷4.2
=(8.08+7.88)÷4.2
=15.96÷4.2
=3.8
(2)(3.75+2.35)×9.9
=6.1×9.9
=6.1×(10-0.1)
=6.1×10-6.1×0.1
=61-0.61
=60.39
(3)12+7.5×36÷7.2
=12+7.5×(36÷7.2)
=12+7.5×5
=12+37.5
=49.5
(4)3.45×0.45+34.5×0.55
=3.45×0.45+3.45×5.5
=3.45×(0.45+5.5)
=3.45×5.95
=3.45×(6-0.05)
=3.45×6-3.45×0.05
=20.7-17.25
=3.45
(5)360÷15-2.5×1.6
=24-4
=20
(6)12.5×25×0.4×0.8
=(12.5×0.8)×(25×0.4)
=10×10
=100
=(8.08+7.88)÷4.2
=15.96÷4.2
=3.8
(2)(3.75+2.35)×9.9
=6.1×9.9
=6.1×(10-0.1)
=6.1×10-6.1×0.1
=61-0.61
=60.39
(3)12+7.5×36÷7.2
=12+7.5×(36÷7.2)
=12+7.5×5
=12+37.5
=49.5
(4)3.45×0.45+34.5×0.55
=3.45×0.45+3.45×5.5
=3.45×(0.45+5.5)
=3.45×5.95
=3.45×(6-0.05)
=3.45×6-3.45×0.05
=20.7-17.25
=3.45
(5)360÷15-2.5×1.6
=24-4
=20
(6)12.5×25×0.4×0.8
=(12.5×0.8)×(25×0.4)
=10×10
=100
点评:此题考查了小数的四则混合运算,注意运算顺序和运算法则,灵活运用所学的运算定律简便计算.
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