解:①(1.2×15+6.4)÷8
=(18+6.4)÷8,
=24.4÷8,
=3.05.
答:商是3.05.
②设这个数为x,可得方程:
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x-
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x=3
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x=3,
x=36.
答:这个数是36.
分析:①1.2乘15的积为1.2×15,其加上6.4的和是1.2×15+6.4,它们的和除以8的商为:(1.2×15+6.4)÷8;
②设这个数为x,则它的
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为
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x,它的
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为
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x,它的
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比它的
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多3,由此可得方程:
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x-
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x=3.
点评:完成此类题目要注意条件中“乘、加上、除以、比”等此类体现数据之间关系及运算顺序的词语.