(78.6-0.786*25+0.75*21.4)/15*1997

squeb2022-10-04 11:39:541条回答

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跑xx道 共回答了18个问题 | 采纳率83.3%
原式=(78.6*0.75+0.75*21.4)/15*1997
=75/15*1997=5*1997
=9985
1年前

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=78.6-78.6*0.25+75%*21.4
=78.6*0.75++75%*21.4
=(78.6+21.4)*0.75
=75
(78.6-0.786×25+75%×21.4)÷15×1997=______.
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解题思路:算式中78.6-0.786×25+75%×21.4可分解为78.6-78.6×0.25+75%(100-21.4),然后再据分配律进行巧算.

(78.6-0.786×25+75%×21.4)÷15×1997
=[78.6-78.6×0.25+75%×(100-78.2)]÷15×1997;
=(78.6-78.6×0.25+0.75×100-0.75×78.2)÷15×1997;
=[(1-0.25-0.75)×78.6+0.75×100]÷15×1997;
=75÷15×(2000-3);
=10000-15;
=9985.

点评:
本题考点: 四则混合运算中的巧算.

考点点评: 完成本题要认真分析试中数据,找出数据之间的内在联系,然后进行巧算.

(78.6-0.786×2.5+0.75×21.4)÷15×1997=?
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(78.6-0.786×2.5+0.75×21.4)÷15×1997
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(1)(78.6-0.786×25+75%×21.4)÷15×2001
(1)(78.6-0.786×25+75%×21.4)÷15×2001
(2)1.65÷(1/4+0.8)-(0.5+13)×(24/35)
(3)[2(5/14)×(2/3)-62.5%]÷[(13/12+6.375)÷11(14/15)]
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计算:(1)(78.6-0.786×25+75%×21.4)÷15×2001(先做括号里的乘法)
=(78.6-19.65+16.05)÷15×2001(再做括号里的加减法)
=75÷15×2001(再做除法)
=5×2001(再做乘法)
=10005
(2)1.65÷(1/4+0.8)-(0.5+13)×(24/35)(小数变分数并约分)
=(33/20)÷(1/4+4/5)-(1/2+13)×(24/35)(括号里的通分相加)
=(33/20)÷(21/20)-(5/6)×(24/35)(除法变乘法、乘法相乘)
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=-10/5907
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=2-{[7/12+1/7]×(10/11)}÷[(12/3)-375/100×(14/5)]
=2-{(61/84)×(10/11)}÷[(12/3)-21/2]
=2-(305/462)÷(-13/2)
=2-(305/462)×(-2/13)
=2+305/693
=2右305/693
(78.6-0.786*25+0.75*21.4)/15*1999
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=(78.6-78.6×0.25+75%×21.4)÷2001
=(78.6×0.75+0.75×21.4)÷2001
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