题目内容

(1)(78.6-0.786×25十75%×21.4)÷15×1997
(2)198÷198
198199
+1÷200
分析:(1)根据算式的特点,把百分数75%转化成小数0.75,然后再根据乘法分配律进行简便计算即可;
(2)根据题意,把198
198
199
改写成繁分数,然后把分子运用乘法分配律化简,再进行计算即可得到答案.
解答:解:(1)(78.6-0.786×25十75%×21.4)÷15×1997
=(78.6-78.6×0.25十0.75×21.4)÷15×1997,
=[78.6×(1-0.25)+0.75×21.4]÷15×1997,
=[78.6×0.75+0.75×21.4]÷15×1997,
=[(78.6+21.4)×0.75]÷15×1997,
=[100×0.75]÷15×1997,
=75÷15×1997,
=5×1997,
=5×(2000-3),
=5×2000-5×3,
=10000-15,
=9985;

(2)198÷198
198
199
+1÷200
=198÷(
198×199+198
199
)+
1
200

=198÷
198×(199+1)
199
+
1
200

=198×
199
198×200
+
1
200

=
199
200
+
1
200

=1.
点评:此题主要考查的整数、小数、分数四则混合运算的运算顺序的应用.
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