考點:小數(shù)四則混合運(yùn)算,運(yùn)算定律與簡便運(yùn)算,分?jǐn)?shù)的四則混合運(yùn)算
專題:運(yùn)算順序及法則,運(yùn)算定律及簡算
分析:(1)根據(jù)乘法分配律進(jìn)行計算;
(2)根據(jù)乘法交換律和乘法結(jié)合律進(jìn)行簡便計算;
(3)把99轉(zhuǎn)化為(100-1)再根據(jù)乘法分配律進(jìn)行計算;
(4)把0.3轉(zhuǎn)化為0.03×10,再根據(jù)乘法結(jié)合律和乘法分配律進(jìn)行計算;
(5)根據(jù)加法結(jié)合律和加法交換律進(jìn)行計算;
(6)根據(jù)加法結(jié)合律和加法交換律進(jìn)行計算;
(7)根據(jù)減法的性質(zhì)進(jìn)行計算;
(8)根據(jù)加法結(jié)合律和加法交換律及減法的性質(zhì)進(jìn)行計算;
(9)根據(jù)減法的性質(zhì)進(jìn)行計算.
解答:
解:(1)0.56×2.7+1.44×2.7
=(0.56+1.44)×2.7
=2×2.7
=5.4;
(2)1.25×2.5×4×0.8
=(1.25×0.8)×(2.5×4)
=1×10
=10;
(3)74×99+5.74
=74×(100-1)+5.74
=74×100-74+5.74
=7400-74+5.74
=7331.74;
(4)72×0.03+0.3×2.8
=72×0.03+0.03×10×2.8
=72×0.03+0.03×28
=(72+28)×0.03
=100×0.03
=3;
(5)
+
+
=
+
+
=1
;
(6)
+
+
+
=(
+
)+(
+
)
=1+
=1
;
(7)
-(
+
)
=
-
-
=1-
=
;
(8)
-
+
-
=(
+
)-(
+
)
=1-1
=0;
(9)
-
-
=
-(
+
)
=
-1
=
點評:本題主要考查了學(xué)生根據(jù)題目特點靈活采用簡便方法進(jìn)行計算的能力.