2和3相乘,分之1 +3和4相乘分之1 +4和5相 - 知识问答

2和3相乘,分之1 +3和4相乘分之1 +4和5相乘分之1= 【用简便方法】

1个回答

1/(2×3)+1/(3×4)+1/(4×5)
=1/2×1/3+1/3×1/4+1/4×1/5
=1/3(1/2+1/4)+1/4×1/5
=1/3×3/4+1/4×1/5
=1/3×3×1/4+1/4×1/5
=1/4+1/4×1/5
=1/4(1+1/5)
=3/10

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