脫式計(jì)算,能簡(jiǎn)算的要簡(jiǎn)算
(1)8.65-3.7+1.35-6.3
(2)[2.1+3.61÷(7.2-5.3)]×30
(3)1.2+36÷[1.44×(0.1-0.05)]
(4)(16.5×3+3×7.5)÷6.
解:(1)8.65-3.7+1.35-6.3
=(8.65+1.35)-(3.7+6.3),
=10-10,
=0;
(2)[2.1+3.61÷(7.2-5.3)]×30
=[2.1+3.61÷1.9]×30,
=[2.1+1.9]×30,
=4×30,
=120;
(3)1.2+36÷[1.44×(0.1-0.05)]
=1.2+36÷[1.44×0.05],
=1.2+36÷0.072,
=1.2+500,
=501.2;
(4)(16.5×3+3×7.5)÷6
=[(16.5+7.5)×3]÷6,
=24×3÷6,
=72÷6,
=12.
分析:根據(jù)題意,由小數(shù)四則混合運(yùn)算的順序,進(jìn)行計(jì)算即可.
點(diǎn)評(píng):根據(jù)題意,先觀察一下能否用簡(jiǎn)便方法計(jì)算,不能用的再按照小數(shù)四則混合運(yùn)算的順序逐步計(jì)算即可.