解:①13.7×0.25×8,
=13.7×(0.25×8),
=13.7×2,
=27.4;
②(
+
)÷
+
,
=
×
+
,
=
+
,
=
;
③7.69×[1÷(
-0.09)],
=7.69×[1÷0.01],
=7.69×100,
=769;
④48×
+53×40%-0.4,
=48×0.4+53×0.4-0.4,
=0.4×(48+53-1),
=0.4×100,
=40.
分析:①利用乘法結(jié)合律0.25×8結(jié)合計(jì)算簡(jiǎn)便;
②先算括號(hào)里的
+
,再算括號(hào)外面的除,最后算加;
③利用加法交換律結(jié)合律,一個(gè)數(shù)連續(xù)減去兩個(gè)數(shù)等于這個(gè)數(shù)減去這兩個(gè)數(shù)的和;
④先算小括號(hào)里的減,再算中括號(hào)里的除,最后算除;
⑤把
,40%,都看做0.4,再利用乘法分配律計(jì)算.
點(diǎn)評(píng):考查了運(yùn)算定律與簡(jiǎn)便運(yùn)算,四則混合運(yùn)算.注意運(yùn)算順序和運(yùn)算法則,靈活運(yùn)用所學(xué)的運(yùn)算律簡(jiǎn)便計(jì)算.