考點(diǎn):整數(shù)四則混合運(yùn)算,運(yùn)算定律與簡(jiǎn)便運(yùn)算
專(zhuān)題:運(yùn)算順序及法則,運(yùn)算定律及簡(jiǎn)算
分析:(1)先算乘法,再算減法;
(2)先算加法,再算乘法;
(3)先算除法,再算減法,最后算乘法;
(4)先算減法,再算乘法,最后算除法;
(5)先算加法,再算除法,最后算乘法;
(6)利用乘法分配律簡(jiǎn)算.
解答:
解:(1)78×34-42×33
=2652-1386
=1266;
(2)54×(25+17)
=54×25+54×17
=1350+918
=2268;
(3)(360-180÷5)×46
=324×46
=14904;
(4)72÷[(26-14)×8]
=72÷[12×8]
=72÷96
=0.75;
(5)[485÷(69+28)]×12
=[485÷97]×12
=5×12
=60;
(6)38×29+38
=38×(29+1)
=38×30
=1140.
點(diǎn)評(píng):整數(shù)混合運(yùn)算的關(guān)鍵是抓住運(yùn)算順序,正確按運(yùn)算順序計(jì)算,適當(dāng)利用運(yùn)算定律簡(jiǎn)算.