题目内容
46+789+54 | 25×28 | 15×13×4 |
421-173-27 | 720÷45 | 420÷35÷2 |
45+208+155 | 23+(159+77) | 6×(19×5) |
25×32×125 | 240÷15÷4 | 129+318+71 |
304+278 | 25×(17×8) | (614+346)÷48 |
考点:整数四则混合运算,运算定律与简便运算
专题:运算顺序及法则
分析:(1)根据加法交换律简算;
(2)先把28分解成4×7,再运用乘法结合律简算;
(3)运用乘法交换律简算;
(4)根据减法的性质简算;
(5)先把45分解成(9×5),再运用除法的性质简算;
(6)根据除法的性质简算;
(7)运用加法交换律简算;
(8)运用加法交换律和结合律简算;
(9)运用乘法交换律和结合律简算;
(10)先把32分解成4×8,再运用乘法结合律简算;
(11)根据除法的性质简算;
(12)运用加法交换律简算;
(13)根据凑整法简算;
(14)运用乘法交换律和结合律简算;
(15)先算小括号里面的加法,再算括号外的除法.
(2)先把28分解成4×7,再运用乘法结合律简算;
(3)运用乘法交换律简算;
(4)根据减法的性质简算;
(5)先把45分解成(9×5),再运用除法的性质简算;
(6)根据除法的性质简算;
(7)运用加法交换律简算;
(8)运用加法交换律和结合律简算;
(9)运用乘法交换律和结合律简算;
(10)先把32分解成4×8,再运用乘法结合律简算;
(11)根据除法的性质简算;
(12)运用加法交换律简算;
(13)根据凑整法简算;
(14)运用乘法交换律和结合律简算;
(15)先算小括号里面的加法,再算括号外的除法.
解答:
解:(1)46+789+54
=46+54+789
=100+789
=889;
(2)25×28
=25×4×7
=100×7
=700;
(3)15×13×4
=15×4×13
=60×13
=780;
(4)421-173-27
=421-(173+27)
=421-200
=221;
(5)720÷45
=720÷9÷5
=80÷5
=16;
(6)420÷35÷2
=420÷(35×2)
=420÷70
=6;
(7)45+208+155
=45+155+208
=200+208
=408;
(8)23+(159+77)
=(23+77)+159
=100+159
=259;
(9)6×(19×5)
=6×5×19
=30×19
=570;
(10)25×32×125
=25×(4×8)×125
=(25×4)×(125×8)
=100×1000
=100000;
(11)240÷15÷4
=240÷(15×4)
=240÷60
=4;
(12)129+318+71
=129+71+318
=200+318
=518;
(13)304+278
=300+4+278
=300+278+4
=578+4
=582;
(14)25×(17×8)
=25×8×17
=200×17
=3400;
(15)(614+346)÷48
=960÷48
=20.
=46+54+789
=100+789
=889;
(2)25×28
=25×4×7
=100×7
=700;
(3)15×13×4
=15×4×13
=60×13
=780;
(4)421-173-27
=421-(173+27)
=421-200
=221;
(5)720÷45
=720÷9÷5
=80÷5
=16;
(6)420÷35÷2
=420÷(35×2)
=420÷70
=6;
(7)45+208+155
=45+155+208
=200+208
=408;
(8)23+(159+77)
=(23+77)+159
=100+159
=259;
(9)6×(19×5)
=6×5×19
=30×19
=570;
(10)25×32×125
=25×(4×8)×125
=(25×4)×(125×8)
=100×1000
=100000;
(11)240÷15÷4
=240÷(15×4)
=240÷60
=4;
(12)129+318+71
=129+71+318
=200+318
=518;
(13)304+278
=300+4+278
=300+278+4
=578+4
=582;
(14)25×(17×8)
=25×8×17
=200×17
=3400;
(15)(614+346)÷48
=960÷48
=20.
点评:此题是考查四则混合运算,要仔细观察算式的特点,灵活运用一些定律进行简便计算.
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