题目内容
递等式计算:(能简算的用简便方法计算)
(1)(5.81-2.09)×3.5
(2)2.5×8×0.5+40
(3)3.865+1.92+3.135+2.08
(4)5.8×6.1+3.2×6.1+6.1
(5)16÷0.25÷0.4
(6)(750-366)÷48×[25÷(210-209)].
(1)(5.81-2.09)×3.5
(2)2.5×8×0.5+40
(3)3.865+1.92+3.135+2.08
(4)5.8×6.1+3.2×6.1+6.1
(5)16÷0.25÷0.4
(6)(750-366)÷48×[25÷(210-209)].
分析:(1)先算小括号里面的减法,再算括号外的乘法;
(2)先算把8分解成4×2,运用乘法结合律简算,再算加法;
(3)运用加法交换了和结合律简算;
(4)运用乘法分配律简算;
(5)根据除法的性质简算;
(6)先计算两个小括号里面的减法,再算中括号里面的除法,然后计算括号外的除法,最后算括号外的乘法.
(2)先算把8分解成4×2,运用乘法结合律简算,再算加法;
(3)运用加法交换了和结合律简算;
(4)运用乘法分配律简算;
(5)根据除法的性质简算;
(6)先计算两个小括号里面的减法,再算中括号里面的除法,然后计算括号外的除法,最后算括号外的乘法.
解答:解:(1)(5.81-2.09)×3.5,
=3.72×3.5,
=13.02;
(2)2.5×8×0.5+40,
=2.5×4×2×0.5+40,
=(2.5×4)×(2×0.5)+40,
=10×1+40,
=10+40,
=50;
(3)3.865+1.92+3.135+2.08,
=(3.865+3.135)+(1.92+2.08),
=7+4,
=11;
(4)5.8×6.1+3.2×6.1+6.1,
=(5.8+3.2+1)×6.1,
=10×6.1,
=61;
(5)16÷0.25÷0.4,
=16÷(0.25×0.4),
=16÷0.1,
=160;
(6)(750-366)÷48×[25÷(210-209)],
=384÷48×[25÷(210-209)].
=384÷48×[25÷1],
=384÷48×25,
=8×25,
=200.
=3.72×3.5,
=13.02;
(2)2.5×8×0.5+40,
=2.5×4×2×0.5+40,
=(2.5×4)×(2×0.5)+40,
=10×1+40,
=10+40,
=50;
(3)3.865+1.92+3.135+2.08,
=(3.865+3.135)+(1.92+2.08),
=7+4,
=11;
(4)5.8×6.1+3.2×6.1+6.1,
=(5.8+3.2+1)×6.1,
=10×6.1,
=61;
(5)16÷0.25÷0.4,
=16÷(0.25×0.4),
=16÷0.1,
=160;
(6)(750-366)÷48×[25÷(210-209)],
=384÷48×[25÷(210-209)].
=384÷48×[25÷1],
=384÷48×25,
=8×25,
=200.
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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