题目内容
用递等式计算.(写出必要的计算过程,能简便计算的用简便方法计算)
7.9×12.5 | 25.38-1.43-4.38-4.57 |
90+10÷0.4×2.5 | 0.8×0.4×(7.6×1.25)×2.5 |
2.3×0.48+0.48×8.7-0.12×4; | 0.1-0.1×[0.01÷(;1-0.9)]. |
分析:(1)根据乘法分配律进行计算;
(2)根据连减的性质进行计算;
(3)先算除法,再算乘法,最后算加法;
(4)根据乘法交换律和结合律进行计算;
(5)根据乘法分配律进行计算;
(6)先算小括号里面的减法,再算中括号里面的除法,再算乘法,最后算括号外面的减法.
(2)根据连减的性质进行计算;
(3)先算除法,再算乘法,最后算加法;
(4)根据乘法交换律和结合律进行计算;
(5)根据乘法分配律进行计算;
(6)先算小括号里面的减法,再算中括号里面的除法,再算乘法,最后算括号外面的减法.
解答:解:(1)7.9×12.5,
=(8-0.1)×12.5,
=8×12.5-1×12.5,
=100-12.5,
=87.5;
(2)25.38-1.43-4.38-4.57,
=25.38-4.38-1.43-4.57,
=(25.38-4.38)-(1.43-4.57),
=21-6,
=15;
(3)90+10÷0.4×2.5,
=90+25×2.5,
=90+62.5,
=152.5;
(4)0.8×0.4×(7.6×1.25)×2.5,
=(0.8×1.25)×(0.4×2.5)×7.6,
=1×1×7.6,
=7.6;
(5)2.3×0.48+0.48×8.7-0.12×4,
=2.3×0.48+0.48×8.7-0.48,
=0.48×(2.3+8.7-1),
=0.48×10,
=4.8;
(6)0.1-0.1×[0.01÷(1-0.9)],
=0.1-0.1×[0.01÷0.1],
=0.1-0.1×0.1,
=0.1-0.01,
=0.09.
=(8-0.1)×12.5,
=8×12.5-1×12.5,
=100-12.5,
=87.5;
(2)25.38-1.43-4.38-4.57,
=25.38-4.38-1.43-4.57,
=(25.38-4.38)-(1.43-4.57),
=21-6,
=15;
(3)90+10÷0.4×2.5,
=90+25×2.5,
=90+62.5,
=152.5;
(4)0.8×0.4×(7.6×1.25)×2.5,
=(0.8×1.25)×(0.4×2.5)×7.6,
=1×1×7.6,
=7.6;
(5)2.3×0.48+0.48×8.7-0.12×4,
=2.3×0.48+0.48×8.7-0.48,
=0.48×(2.3+8.7-1),
=0.48×10,
=4.8;
(6)0.1-0.1×[0.01÷(1-0.9)],
=0.1-0.1×[0.01÷0.1],
=0.1-0.1×0.1,
=0.1-0.01,
=0.09.
点评:四则运算,先弄清运算顺序,然后再进一步计算,能简算的要简算.
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用递等式计算.(写出必要的计算过程,能简便计算的用简便方法计算)
7.9×12.5 | 25.38-1.43-4.38-4.57 |
90+10÷0.4×2.5 | 0.8×0.4×(7.6×1.25)×2.5 |
2.3×0.48+0.48×8.7-0.12×4; | 0.1-0.1×[0.01÷(;1-0.9)]. |