题目内容
递等式计算(能简便的用简便方法计算). 99×38 | 125×56 | 5500÷125 |
345+655×240 | 478-156-144 | 899-(253+299) |
[400-(678+312)÷330]×250 | 9800÷(25×49) | 48400÷25÷4 |
8400÷(21×74+26×21) |
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)先把99分解成(100-1),再运用乘法分配律简算;
(2)先把56分解成8×7,再运用乘法结合律简算;
(3)先把125分解成5×5×5,再运用除法的性质简算;
(4)先算乘法,再算加法;
(5)(6)根据减法的性质简算;
(7)先算小括号里面的加法,再算中括号里面的除法,然后根据乘法分配律简算;
(8)(9)根据除法的性质简算;
(10)先运用乘法分配律简算,再算除法.
(2)先把56分解成8×7,再运用乘法结合律简算;
(3)先把125分解成5×5×5,再运用除法的性质简算;
(4)先算乘法,再算加法;
(5)(6)根据减法的性质简算;
(7)先算小括号里面的加法,再算中括号里面的除法,然后根据乘法分配律简算;
(8)(9)根据除法的性质简算;
(10)先运用乘法分配律简算,再算除法.
解答:
解:(1)99×38
=(100-1)×38
=100×38-1×38
=3800-38
=3762;
(2)125×56
=125×8×7
=1000×7
=7000;
(3)5500÷125
=5500÷(5×5×5)
=5500÷5÷5÷5
=1100÷5÷5
=220÷5
=44;
(4)345+655×240
=345+157200
=157545;
(5)478-156-144
=478-(156+144)
=478-300
=178;
(6)899-(253+299)
=899-299-253
=600-253
=347;
(7)[400-(678+312)÷330]×250
=[400-990÷330]×250
=[400-3]×250
=400×250-3×250
=100000-750
=99250;
(8)9800÷(25×49)
=9800÷49÷25
=200÷25
=8;
(9)48400÷25÷4
=48400÷(25×4)
=48400÷100
=484;
(10)8400÷(21×74+26×21)
=8400÷[21×(74+26)]
=8400÷(21×100)
=8400÷2100
=4.
=(100-1)×38
=100×38-1×38
=3800-38
=3762;
(2)125×56
=125×8×7
=1000×7
=7000;
(3)5500÷125
=5500÷(5×5×5)
=5500÷5÷5÷5
=1100÷5÷5
=220÷5
=44;
(4)345+655×240
=345+157200
=157545;
(5)478-156-144
=478-(156+144)
=478-300
=178;
(6)899-(253+299)
=899-299-253
=600-253
=347;
(7)[400-(678+312)÷330]×250
=[400-990÷330]×250
=[400-3]×250
=400×250-3×250
=100000-750
=99250;
(8)9800÷(25×49)
=9800÷49÷25
=200÷25
=8;
(9)48400÷25÷4
=48400÷(25×4)
=48400÷100
=484;
(10)8400÷(21×74+26×21)
=8400÷[21×(74+26)]
=8400÷(21×100)
=8400÷2100
=4.
点评:本题考查了四则混合运算,注意运算顺序和运算法则,灵活运用所学的运算定律进行简便计算.
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