题目内容
计算 1.135+3.346+5.557+7.768+9.979=
27.785
27.785
．分析：观察算式发现，把7.768分成5.557+2.211，把9.979分成5.557+4.422之后，再把拆成的4.422和2.211分别与算式前面的两个小数相加凑成5.557，进而利用乘法分配律进行巧算．
解答：解：1.135+3.346+5.557+7.768+9.979，
=1.135+3.346+5.557+（5.557+2.211）+（5.557+4.422），
=1.135+3.346+5.557+5.557+2.211+5.557+4.422，
=（1.135+4.422）+（3.346+2.211）+5.557+5.557+5.557，
=5.557+5.557+5.557+5.557+5.557，
=5.557×5，
=27.785；
故答案为：27.785．
=1.135+3.346+5.557+（5.557+2.211）+（5.557+4.422），
=1.135+3.346+5.557+5.557+2.211+5.557+4.422，
=（1.135+4.422）+（3.346+2.211）+5.557+5.557+5.557，
=5.557+5.557+5.557+5.557+5.557，
=5.557×5，
=27.785；
故答案为：27.785．
点评：此类型的题目可根据算式中加数的特点，采用凑数法进行巧算．
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