解:(1)
÷(
+
)×
,
=
×
,
=
,
=
;
(2)3
×7.4-3
+3.6×3.125,
=3.125×(7.4+3.6-1),
=3.125×10,
=31.25;
(3)42
÷7,
=(42
)×
,
=42×
,
=6
,
=6
;
(4)52.75-
-9.625,
=52.75-(0.375+9.625),
=52.75-10,
=42.75.
分析:(1)
÷(
+
)×
,根據(jù)分?jǐn)?shù)混合運(yùn)算的運(yùn)算順序,按照分?jǐn)?shù)四則運(yùn)算的計(jì)算法則進(jìn)行簡(jiǎn)算;
(2)3
×7.4-3
+3.6×3.125,把分?jǐn)?shù)化成小數(shù),再運(yùn)用乘法分配律進(jìn)行簡(jiǎn)算;
(3)42
÷7,將原式轉(zhuǎn)化為:(42
)×
,再運(yùn)用乘法分配律進(jìn)行簡(jiǎn)算;
(4)52.75-
-9.625,把
化成小數(shù)0.375,再意義減法的運(yùn)算性質(zhì)進(jìn)行簡(jiǎn)算.
點(diǎn)評(píng):此題主要考查分?jǐn)?shù)四則混合運(yùn)算,要求學(xué)生牢固掌握運(yùn)算順序和計(jì)算法則,并且能夠靈活運(yùn)用運(yùn)算定律進(jìn)行簡(jiǎn)便計(jì)算.