?递等式计算:(能简便的要简便)
×7?????????????(+1÷)÷9×××+×?2.35+÷+2.35????????? (+)÷(-) (+)÷(+-)÷25÷(-)
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解:(1)3×7,
=(3×7)+(×7),
=21+,
=21;???
(2)()÷,
=(+1×)×,
=(+)×,
=4×,
=,
=1;?????
(3)9××,
=9××,
=;
(4)×+×,
=()×,
=1×,
=;???????????
(5)2.35++2.35,
=2.35++2.35,
=2.35+2+2.35,
=6.7;??????????????
(6)()÷(),
=÷,
=×,
=,
=;
(7)(),
=()×,
=,
=2,
=;????????????????????
(8)(),
=24+×24-×24,
=18+4-3,
=19;???????????????
(9)25÷(),
=25÷(),
=25×,
=180.
解析分析:(1),把看作(3),利用乘法分配律比较简便;
(2)()按运算顺序直接计算就可以了;
(3)9×先约分,再计算;
(4),利用乘法分配律比较简便;
(5)2.35++2.35按运算顺序计算;
(6)()÷(),先通分,再计算;
(7)(8)()、()先转化成乘法,再利用乘法分配律比较简便;
(9)25÷(),先通分,再计算.
点评:计算这类题目,先要认真观察算式特点,能简算的要简算,不能简算按照混合运算的计算方法进行计算,要灵活处理,分别对待.