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】
问题描述：
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】
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